Size 4.5 ball
My thoughts and a little bit of research. It's a long read and it took some time, so let's dig in.
The size 4.5 ball has come back into the spotlight recently, due to the announcement of it’s use in the upcoming WXV Global Series.
The ball has had some trials across the HSBC SVNS, U18s and U20s international competitions, domestic competitions in Spain and Colombia and elite domestic club training sessions.1
Upon it’s announcement Zoe Harrison, Red Roses Fly-Half, called it the “worst decision someone has ever made”.2 Trialling it in a major tournament that has ramifications upon world rankings is what some people are finding problematic. Others have issue with the total idea of the ball size change.
The ball:
Same weight as a size 5
3% smaller than a size 5
Weight was changed after a trial in the U18s Six Nations tournament
This is a contentious issue. Zoe Harrison and others are firmly on the con side. Former player Shaunagh Brown released a statement on Instagram on the pro side, saying why not try it, citing the size difference between men’s and women’s hands.
Is Rugby On It’s Own?
If the ball change is rolled out across the sport, rugby union will not be isolated in it’s decision. There are size modifications in different sports, including cricket, athletics, basketball and handball:
In cricket, the men’s ball must weigh between 155.9g and 163g must have a circumference between 22.4 cm and 22.9 cm. The ball in women’s cricket must weigh between 140g and 151g and have a circumference between 21.0 cm and 22.5 cm.3
In the 400m hurdles in athletics , the hurdles in the men’s race are 91.4cm in height. In the women’s race they are 76.2cm.4
In handball, the weight and circumference rules change depending on whether the ball is resin or non-resin. For both categories of ball type, female players use a lighter and smaller ball.5
In water polo, the men’s ball must have a circumference between 680mm and 710mm and the women’s ball must be between 650mm and 670mm.6
In basketball, all male players aged 14 and above use a size 7 ball and all female players aged 14 and above and male players aged 12-14 use a size 6 ball.7 The smaller size ball was introduced in the 2004/2005 season.
I want to look into the affects of a smaller ball in other sports. I did a quick search to see if other sports had published research into the differences of ball size and the impact upon skills. I couldn’t find much (this is not to say there isn’t research, just that it’s not accessible, published in a journal or easily found via some searches).
I’ve found some recent research that looked into the smaller ball size in basketball. Full disclaimer, there are other published papers, a few that are pre-1990. I’ve tried to stick to more a recent source so that it’s research that’s been conducted on the newer ball. (There were a few ball changes in 1974 and 1984 from what I can gather)
A study published in 2012 stated that the smaller size of ball did not improve in shooting accuracy. It’s important to note that this study looked at shooting and not other skills affected by the ball change, such as dribbling and passing. The study concludes that the introduction of a new ball may not have been fully needed within women’s basketball.
“Given the characteristics of the male and female body – primarily the gender-related difference in strength – the introduction of a smaller and lighter ball is an understandable and expected change. Despite all reasons in favour of introducing the size 6 basketball, the use of the smaller and lighter ball clearly does not improve shooting accuracy. It may be concluded that shooting accuracy is a complex issue that depends on a large number of factors, only some of which have been addressed in our study.” - The Effect of Introducing a Smaller and Lighter Basketball on Female Basketball Players’ Shot Accuracy
Another study published in 2016 looked into the effects of using a lighter and smaller ball in women’s football. The researchers did state that this is a small study, so there might be some differences that emerge with a larger study. However, in their research, was no difference in the number of passes (including short, medium or long passes). There was a higher kicking speed when using the lighter ball.
As well as measuring passes, the study looked at average heart rate. There was no differences in mean heart rate during match play when using either ball. The study concluded that there was no technical or physical differences in match play between the two balls.
“However, the lack of differences in the types of passes, shots on goal and number of headers, combined with the fact that 7 of the investigated players performed most sprinting in the game with the standard ball, underlines that introducing a smaller, lighter football has no systematic and revolutionary effects on match performance in high-level adult female footballers.” - Kicking Velocity and Effect on Match Performance When using a Smaller, Lighter Ball in Women’s Football
What Does The Current Data From Rugby Tell Us?
It is important to note that World Rugby are responding to the trials. You can see some of their data here. (Thanks to YSC for linking this in their article). That data is from 2024 and mentions the ball being lighter. They subsequently changed the weight of the ball after the U18s Six Nations tournament.
I want to briefly examine men’s and women’s rugby to see what the current state of play is.
Let’s compare some data from some men’s and women’s competitions. It’s important to state here that this data is from the elite game.
World Rugby’s Blueprint For Growth8 looked at some playing statistics from the 2021 and 2025 Women’s World Cups. There were increases across different aspects of play:
Average tries per match increased by 30%
Successful kick penalty rate increased by 11%, to 85% success rate
Average ball in play time increased to 36 mins
Let’s compare those to the stats from the Men’s Rugby World Cup in 2023:
50 penalties were missed, approximately 34%9
This means the tournament had a 66% penalty success rate
Ball in play time was 34 mins10
It’s important to state that these stats are snapshots that tell one particular story about elite international men’s and women’s rugby. For example: the penalty kick stats from the women’s World Cup don’t tell me where those kicks were taken from.
However, the ball in play stat is key. Women’s rugby has a higher ball in play time. This means more rugby for the fans.
World Rugby cited fewer knock ons and more tries as some of the fundamental reasons for the trial. However, YSC went through further data in their article and cited faster ruck speeds, more tries and fewer knock ons in the 2025 Women’s World Cup compared to the recent 2023 Men’s tournament. The caveat here is that this data is from the elite game and a ball change would presumably affect all levels of the sport, but this is our main source of data.
If the aim is to take fundamental elements of the women’s game (more tries, higher ball in play time) and advance those features, then that should be spoken about.
Introducing a trial as potentially enhancing the USP of women’s rugby, might have been received differently.
Framing something as a solution to a negative, when some of the data suggests otherwise, becomes problematic.
Why Change It?
If it isn’t broke don’t fix it. This is a comment that I’ve heard alot, and they’re not wrong (especially when data from others sports potentially suggests that a ball size doesn’t work within an elite level).
There are also other pressing issues that could be examined first within women’s rugby. Is this an invented problem? Is it an immediate problem?
As of 2025:11
Women’s rugby brings £6.7b in value to society
There are 7.3m W&Gs players across the globe
65% of women’s rugby fans have increased their engagement
29% of womens rugby fans are under 35 years old, compared with 25% of men’s rugby fans
43% of women’s rugby fans are female, compared to 39% of men’s rugby fans
The growth of women’s rugby is outpacing men’s rugby. Fans of women’s sport, including women’s rugby, care about all aspects of the sport, not just the on-field play.
In a women’s rugby report, published in 2025, the top things fans said they cared about were: the growth and development of women’s rugby, positive representation of women in sports, enjoyment of the style of play and supporting gender equality in sport.
These are all aspects of the game that could be affected positively or negatively by the ball change.
If women’s rugby is growing on and off pitch, then why is the change needed? A smaller ball is intended to improve accuracy of passing. Is that a problem within women’s game? Is a ball change the easy solution or the best solution?
The increases in ball in play time, kicking and tries per match average from the 2021 to the 2025 World Cup, were all done without a ball change. I would argue that increased investment, a focus on pathways and coaching workforce led to those positives.
What Are The Implications?
I can see the reasons for a trial. I understand the average size difference in men’s and women’s hands and how that might lead towards a trial of a smaller ball. I also definitely believe in equity.
However, I have some main concerns, especially around the grassroots game, and I’m going to try and organise these as best as I can.
Stealth Tax:
A rollout of a new ball size immediately means additional costs for clubs. For some elite clubs and top tier international set ups, this cost will be manageable.
However, every grassroots club that has a W&Gs side that requires a 4.5 ball, will need to purchase new balls. It’s true, that rugby clubs will purchase alot of new balls in the off season to ensure their club has good equipment. However, the introduction of the 4.5 will require purchasing a complete set for their W&Gs set up. This means multiple sets if they have more than one female team.
As of October 2025, there are approximatley 500 clubs in England offering women’s and girls’ rugby12. Not all of them will have a women’s side, but girls will probably start using size 4.5 in the U16s age bracket.
Each team needs approx 10 balls for training. They also need a match ball. Let’s say 1 match ball (although ideally you need approx 2-3). Clubs may purchase a number of new balls each season for their teams. Normally this is done by checking which balls are fine, which one’s aren’t and ordering replacements for the ones that aren’t useable. With the change, they will have to buy a new complete set of balls.
On Gilbert’s website (the manufacturer of the size 4.5), a size 4 rugby ball is £19.99 and a size 5 is £20.99. So, for now, let’s estimate the cost of the 4.5 as £20 (the cost of the 4.5 wasn’t visible in the shop). A match ball will approximatley cost £31.1913
This means that each club will have to spend a minimum of £231.19 for 10 training balls and 1 match ball. If there’s more than one team that requires a 4.5 size ball (U16s, U18s 2XV women’s team or 1XV women’s team), then they will have to purchase more - unless they want to share the new balls which seems like a logistical nightmare and hardly fair.
If you take that minimum purchase that each club will need to make and multiply it by 500 (the number of clubs with W&Gs teams in England). The spend for England is £115, 595. That amount is a minimum estimate (and maths is not my strength).
This feels like an accidential stealth tax on any club with a female team. It can be a hard enough battle to set up, run and finance a female team in a male-dominated sport. Yes, things are improving. However, this feels like an additional battle volunteers and players may have to fight at some clubs.
The Struggle with Perceptions
“Do you do contact, do you tackle?” “You don’t play on a full sized pitch?” “It’s not real rugby as you don’t tackle or use a full pitch.”
These are some of the comments I’m used to hearing, especially in my playing days. It always surprised people when I remarked that women did indeed tackle, scummage, it was full contact and on a full size pitch too - shock horror! I’ve noticed the frequency of these comments decreasing as the Red Roses have grown in popularity.
However, I fear that using a different sized ball will open the door to some of these comments and negative perceptions of women’s rugby - that it’s not “proper rugby.”
Is this a strong enough reason to not change something? No. Comments from bigots should never dictate a decision. Some people will find a way to undermine women’s sports regardless.
Any programme, across any sport, that is well-researched and equitable should be implemented regardless of misogynists or people that hold static views.
However, I don’t want an equipment change to undermine so much of the progress and amazing work that has happened over decades. I will admit it scares me. This feels like the next great test for sport and women’s rugby. It also reinforces the need for transparency in this decision and trial.
Conclusion
I’ve taken some time to dig through some research, articles and data. I’ve looked at rugby and other sports. It’s difficult to summarise but I wanted to end with some of my own thoughts/statements.
I support any women’s sport questioning the current ways of doing and not copying and pasting what’s been done before.
I’m also thinking about the need for innovation in our sport, across both men’s and women’s rugby.
I’m thinking about the the benefits of clear, concise and publicly available data.
I keep thinking about the often used statement: “women are not small men”. I wonder where this decision fits into that thinking. Does it support it or not?
I’m also thinking about the money invested into the trial and wonder whether what the impact would be if it was invested into coach development instead.
I’m also thinking about the different journeys male and female players often take in being physically active, finding sport and finding rugby.
I’m thinking about the professionalisation of women’s rugby and how few of our elite players are paid full time for their rugby careers.
I would love World Rugby to release some of the data of the trials. Let’s compare the SVNS and WXV trials to existing years and other competitions. Transparency is vital especially if World Rugby wish to make this change across women’s rugby.
World Rugby’s own targets include 3.4 million women and girls playing rugby by 202914 and continuing to grow the playing pathways (including school and social rugby)15.
Women’s rugby needs to be convinced that these trials and this potential change would fundamentally enhance the sport. It needs to be convinced that this trial is one of the immediate concerns of the sport, and how it can help World Rugby achieve it’s targets for growth. It also needs to be convinced that the players asked for this.
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https://www.svns.com/en/news/1018923/world-rugby-expands-trials-of-a-new-ball-for-womens-rugby-to-hsbc-svns
https://www.bbc.co.uk/sport/rugby-union/articles/ckgpn3pdzr7o
https://www.lords.org/mcc/the-laws/the-ball
https://www.olympics.com/en/news/athletics-track-and-field-sprints-marathons-jumps-throws-heptathlon-decathlon
https://www.olympics.com/en/news/handball-game-rules-regulations-how-to-play
https://www.barnetwaterpolo.com/journal
https://shop.basketballengland.co.uk/pages/basketballs-size-chart
https://resources.worldrugby-rims.pulselive.com/worldrugby/document/2026/04/07/e8975add-b291-4da3-89f9-1dd2bd2d74d3/A-Blueprint-For-Growth-Report-Second-Edition-Spring-2026-Final.pdf
https://www.data-ruck.com/blog/predicting-kicks-outcome/
https://www.researchgate.net/figure/The-Average-Ball-in-Play-Per-Game-of-the-Rugby-Union-World-Cup-across-Years-of_tbl1_384103809
https://resources.worldrugby-rims.pulselive.com/worldrugby/document/2026/04/07/e8975add-b291-4da3-89f9-1dd2bd2d74d3/A-Blueprint-For-Growth-Report-Second-Edition-Spring-2026-Final.pdf
https://www.englandrugby.com/follow/news-and-media/rfu-launches-action-plan-power-womens-and-girls-rugby-2030
https://www.gilbertrugby.com/collections/rugby-balls
https://www.facebook.com/reel/1459980909068823
https://www.world.rugby/news/1002587/world-rugby-launches-a-blueprint-for-growth-womens-rugby-the-most-comprehensive-fan-data-and-commercial-analysis-ever-undertaken-in-the-womens-game
Really well-researched take on a genuinely complicated conversation. The data comparison across sports alone makes this worth reading twice. Great read!
Great article Jesc. Having seen a number of highly entertaining matches at the recent World Cup (with you) I just can’t fathom what problems exist that changes to the ball size will fix.