The measurement is volume
Length fools people. Shoulder-length straight hair packs into a fist. Shoulder-length braids do not. A low ponytail that looks long in the mirror is still a small lump once you twist it up. Locs, weaves, and a dense afro are the lump. The cap fails on bulk, then everyone blames "long hair" and buys another skull-shaped silicone from the vending machine.
Put the hair where it will live in the water before you shop. High bun or folded locs at the crown, not a tail sitting on the neck. Then look at the lump. If it is bigger than a clenched fist, a standard adult cap is a waste of money. Stretching silicone until it screams is how you get a tear at the ear and a soggy bun on length one.
This is not a poster about who is allowed in the sport. It is kit. Hair that takes up space needs a cap with a pocket at the back, a wider opening, and silicone thick enough not to split when you drag it over clips. If the opening will not pass the bun, stop. Size up. Do not "make it work" with talc and hope.
What still gets wet
Makers love the word waterproof. Hair under a cap is not a phone in a pouch. Water finds the hairline, the temples, and any gap you left when you trapped a bubble at the crown. A dive and a tumble turn shove more in. After a 4,000-metre set the edges of the style will be damp even in a good extra-large. The middle of the bun can stay much drier than it would in a skull cap. That is the win. Bone-dry after fly 200s is a lie.
Chlorine still sits on the hairline you did not seal. Rinse. Condition. A pocket that is too big sloshes, balloons, and drags. If you can pinch a fist of air at the nape after you put it on, you went up a size too far or you skipped the burp.
A cap that promises bone-dry locs through diving and flip turns. Silicone is a seal, not a submarine hatch. If dryness is the only job and you are floating in a holiday pool, a satin-lined leisure cap with a clasp is more honest. If you are training, buy extra-large silicone and expect a wet hairline.
Soul Cap sizes in centimetres
Soul Cap's large swim cap is 100% silicone, latex-free, sold in M, L, XL, and XXL. The brand was built for afro hair and the styles that come with volume. I care about the printed millimetres more than the slogan. On 23 August 2026 the official product page listed:
| Soul Cap size | Height × width × opening | Their own hair note |
|---|---|---|
| M | 23 cm × 25 cm, opening 18.5 cm | Straight or fine hair past the shoulders |
| L | 24 cm × 28.5 cm, opening 19 cm | Curly, bouncy, or afro hair above the shoulders |
| XL | 28.5 cm × 31 cm, opening 22 cm | Braids or locs that sit above the shoulders |
| XXL | 35.5 cm × 31 cm, opening 23 cm | Braids, locs, curls, or afro hair past the shoulders |
That mapping is from Soul Cap's own size editorial, not a review score. Read it as a starting guess. A short, dense loc style can still need XL. Fine waist-length hair can live in M. If you are between sizes, the reviews on their own shop are full of people who ordered XXL, found it baggy, and went down. Baggy wets you. Tight tears. Fit the bun you actually swim in, not the hair on a good-photo day.
They also sell a smaller Regular for short, low-volume hair. If someone in the family has a fade, that is the other object. Do not put a Regular on box braids because it was in the same parcel.
On 23 August 2026 the UK shop showed the large cap around £19. The US product page showed about $20. Contrast and bold-logo versions sat a few pounds or dollars higher. Resellers wandered from about £15 to about £25 depending on colourway. Treat those as ranges. Check the till before you buy.
Height is the pocket. Opening is whether you can get the bun in without a fight. XL jumps to 22 cm. XXL is only 1 cm wider at the mouth and much taller. If the struggle is the opening, not the length of the locs, XL may be enough. If the locs hang past the shoulders once folded, pay for the extra height.
Other extra-large silicone, without the brand fog
Soul Cap is not the only extra-large. It is the one that publishes a centimetre chart for protective styles. Speedo sells two different "long hair" stories, and mixing them up is how people buy the wrong one twice.
Speedo's Silicone Long Hair Cap is extra space to tuck a ponytail. One size. About $18 to $22 on Speedo USA when I checked on 23 August 2026, sometimes on offer. Fine for long, relatively flat hair. Not a loc cap. If your bun looks like a second head, skip it.
The volume Speedo is the Biofuse Protective Cap. Speedo UK copy says Size L is a 94% volume increase versus their silicone moulded cap, and Size XL is a 154% increase. Elastomeric silicone, textured inside. About £19 on Speedo UK, about $22 to $28 in US shops that still stock it. A real extra-large from a big brand. Waist-length braids still often need more pocket than that hang-tag percentage. If Soul Cap XXL is the only thing that has ever gone on, believe your bathroom.
Hairbrella's satin-lined swim cap is a different job. Official price $44 USD on 23 August 2026, with sale colours sometimes nearer $34. Classic band 43 to 56 cm. XL band 51 to 61 cm, sold for larger heads, thick hair, and protective styles up to about 18 inches. Adjustable clasp. Satin lining. I would use it in a hotel pool when the only goal is less chlorine in the style. I would not take the clasp to marshalling and expect a wrinkle-free profile. Comfort is not hydrodynamics.
Marketplace "XXL for dreadlocks" listings often copy Soul Cap's words and skip the millimetres. If you cannot see height, width, and opening, you are guessing.
Two caps, for volume, not for club print
The other Finzy cap page uses two caps as club colour outside and a smooth race cap inside. That is a marshalling trick. Volume two-cap is a different stack.
Inner cap holds the bun so it does not slump toward the neck. A thinner silicone, or a liner you can get over the hair without a wrestling match, is enough. Clip or twist first. The inner layer is furniture.
Outer cap is the extra-large silicone. Forehead edge on first, then pull the pocket over the bun, then burp the air at the nape until the seal sits on skin at the hairline and ears. Goggles over the outer edge so the strap does not peel the cap off on the dive.
World Aquatics Competition Regulations, Part One, article 7.7.9 allow one cap or two. Both must meet the cap rules, including a 2 mm maximum thickness. That is permission, not a promise your XXL-plus-latex sandwich is legal at every gala. A standard printed club cap stretched over a volume pocket is the usual split. If the squad wants colour on the block, you need an extra-large in a colour the marshal will accept, or you ask before the meet. Do not find out in the call room.
Hold, then seal, then burp. A second tiny cap on the outside is not a method. It is how extra-large silicone dies.
Training nights versus the block
For club training the test is simple. Does it go on? Does it stay on through a tumble turn? Can you hear the coach? Drag from a pocket is real and mostly irrelevant on a Tuesday aerobic set. Buy the cap you can put on without a parent and a bottle of baby powder in the changing room.
Racing is pickier. World Aquatics still wants a cap that follows the natural form of the head. That sentence is why FINA refused Soul Cap around the Tokyo Games, then added it to the approved list in September 2022 after a review. The BBC report is the public record. I am not turning that into a speech. For a swimmer with volume hair it means: check the current approved-swimwear list if you are on a World Aquatics start list, burp the pocket so you are not racing a balloon, and do not assume a satin clasp cap is a race cap because it kept a holiday braid dry.
Most club galas will not weigh your cap. They will notice if it comes off on the dive. Practise the put-on at home until it is boring. Pack a spare extra-large. One tear and you are back to a skull cap that never fitted.
Prices as ranges, checked 23 August 2026
Kit prices move with colourways and sales. These are the official and near-official numbers I could see on 23 August 2026, written as ranges on purpose.
| Cap | Job | About, 23 Aug 2026 |
|---|---|---|
| Soul Cap Large, M to XXL | Protective-style pocket. The centimetre chart | £15 to £25 / about $20 on soulcap.com |
| Speedo Biofuse Protective L / XL | Big-brand extra volume. 94% / 154% vs moulded | About £19 UK / $22 to $28 US |
| Speedo Silicone Long Hair | Tucked ponytail. Not locs | About $18 to $22 US |
| Hairbrella satin-lined | Leisure dryness, clasp, lining | About $34 to $44 USD on hairbrella.com |
A volume cap at £19 that you can actually wear is cheaper than four skull caps in the bin. It is still not a reason to skip conditioner. Chlorine at the hairline does not care what you spent.
What goes in the bag
Extra-large silicone needs its own pouch so zips and keys do not bite it. Pack a spare of the same size. Powder or a drop of water helps the put-on. A microfibre wrap for after. The rest of the meet bag is on the gala packing list. Practise the put-on at home. Volume is slower on poolside. After the heat, type the time.
Buy the pocket that goes on. Then log the session. A perfect extra-large cap will not remember the 100 fly. Finzy will. Different objects. Same Tuesday.
