Buying a rash guard should be simple.
It's a tight shirt.
You put it on. You grapple. Ideally, it prevents your nipples from being sanded off by a sweaty puzzle mat.
And yet somehow the combat sports industry has turned buying one into a technical briefing from NASA.
Four-way stretch. Moisture management. Performance compression. Anatomical panel construction. Advanced moisture-wicking combat technology forged beneath a blood moon by Japanese textile monks.
Relax.
You need a rash guard that fits properly, survives people trying to fold you into carry-on luggage, doesn't ride up to your armpits, and preferably makes you look dangerous enough that the new guy chooses somebody else for his first round.
Here's how to choose one.
First: What Does a Rash Guard Actually Do?
A rash guard puts a layer of stretchy technical fabric between your skin and everything trying to ruin it.
In BJJ and grappling, that means mats, friction, Velcro, fingernails and Derek—the 104kg white belt who describes every roll as "flowy" immediately before attempting to powerbomb your skeleton.
A proper grappling rash guard should fit close to the body, move with you and manage sweat without turning into a loose wet T-shirt halfway through training. Flat seams are also common because raised seams rubbing against your skin for six rounds are approximately as enjoyable as explaining to your girlfriend why another man's beard has given you neck burn.
For no-gi competition, your rash guard can also be part of the required uniform. Under current IBJJF rules, no-gi competitors must wear a skin-tight elastic shirt long enough to reach the shorts waistband. The permitted colors are black, white, black-and-white, or 100% rank color, with at least 10% of the athlete's belt-rank color when applicable.
So yes, sometimes the shirt matters.
Let's buy the right one.
1. Get the Fit Right
This is the most important part.
A grappling rash guard should fit snugly against your body without restricting your movement. It shouldn't hang like a football shirt, but you also shouldn't need three teammates, petroleum jelly and instructions from the local fire department to get into it.
Too loose and the material can bunch, twist and ride up during scrambles.
Too tight and you'll spend warm-up wondering whether your liver is supposed to have a pulse.
The sweet spot is compression without restriction.
Raise your arms. Rotate your shoulders. Mimic a frame. Throw an imaginary underhook at an innocent household appliance.
If the rash guard stays against your torso and you can move normally, you're close.
And don't automatically buy your normal T-shirt size. Check the manufacturer's size chart and use your actual measurements. Rash guard cuts differ between brands, and "I'm always a Large, bro" is not an internationally recognized unit of measurement.
2. Choose Fabric That Can Survive Grappling
Your regular gym compression shirt and a grappling rash guard may look suspiciously similar.
Then somebody grabs you, twists you, puts 90kg through your shoulder and drags the fabric sideways while you're reconsidering every decision you've made since childhood.
Now we find out what you bought.
For grappling, look for a stretchy synthetic blend—commonly polyester with elastane/spandex—with good shape recovery. Construction matters because BJJ repeatedly stretches the material in several directions under load. Current rash-guard buying guides commonly emphasize durable synthetic blends, four-way stretch and reinforced construction for precisely this reason.
You may also see GSM mentioned.
That means grams per square metre: essentially a measurement of fabric weight. A higher number generally means heavier fabric, but don't fall into the extremely MMA trap of deciding that therefore MORE NUMBER = MORE BETTER.
A heavier rash guard can feel substantial and durable but may also run hotter. A lighter one can feel cooler but needs good construction to withstand repeated grappling.
Fabric quality, stretch recovery, stitching and fit matter together.
It's a rash guard, not an RPG character. You don't win because yours has +17 GSM.
3. Look at the Seams
Nobody gets excited about stitching.
Until it sucks.
Then you'll think about stitching for the entire session because one seam has spent 45 minutes slowly sawing through your armpit.
Flatlock seams are particularly useful in rash guards because the seam sits flatter against the body, reducing bulky ridges and potential friction points. They're also widely recommended in grappling-specific gear because the garment is constantly stretched and loaded during training.
Look around the shoulders, armpits and side panels.
Those areas get abused.
If the stitching looks like somebody assembled the shirt at 4:57 p.m. on a Friday while already mentally inside the pub, perhaps continue shopping.
4. Long Sleeve or Short Sleeve?
This causes far more debate than necessary.
Long sleeves give you more coverage.
Short sleeves give you less coverage.
Thank you for attending my TED Talk.
Long-sleeve rash guards put more fabric between your arms and the mat, which can be useful if you're prone to friction burns or simply prefer maximum coverage. They're also nice in colder gyms.
Short sleeves generally feel cooler and give you that liberating sensation of displaying your forearms to everyone.
Which one is "better"?
Neither.
For BJJ and grappling, choose based on your training environment and preference. Some people hate feeling fabric around their wrists. Others want as little exposed skin touching the mats as possible.
Personally, if your academy mats feel like they're made from recycled cheese graters, long sleeves suddenly become a compelling technological innovation.
5. Make Sure It Doesn't Ride Up
There is a particular type of rash guard that begins training at your waist and finishes the round underneath your nipples.
This is known scientifically as a shit rash guard.
Look for adequate torso length and a cut designed to stay close around the waist. Some designs add silicone or rubberized grip bands around the inside hem to help keep the shirt planted.
That's useful during grappling because you're constantly bridging, shrimping, inverting and having another adult attempt to remove your spine through your mouth.
A slightly longer athletic cut can also help.
Your rash guard should stay approximately where you put it.
A revolutionary concept.
6. Sublimation Beats Graphics That Give Up
You've found the perfect design.
A roaring samurai gorilla is fighting a cybernetic shark while lightning strikes Mount Fuji.
Obviously you need it.
But check how the artwork is applied.
Sublimation printing puts the design into the synthetic fabric rather than leaving a thick graphic sitting on top of it. That's why it's so popular for grappling gear: there isn't a large surface print waiting to crack or peel after repeated stretching and washing. Grappling gear guides routinely recommend sublimation for that durability advantage.
That doesn't mean every non-sublimated detail instantly explodes.
It means that when you're buying something designed to be stretched, sweated in and washed constantly, permanent dyed graphics make a lot of sense.
Especially if you've paid good money for that cyber-shark.
He deserves longevity.
7. Competition Rash Guards Are a Different Problem
If you're competing, stop shopping purely with your eyeballs.
Check the rules of the actual organization and event you're entering.
For current IBJJF no-gi competition, rash guards must meet specific color and rank requirements. The shirt must be elastic and skin-tight, cover the torso to the waistband, and comply with the permitted black/white/rank-color scheme.
There can also be event-specific requirements. For example, the 2026 European IBJJF No-Gi Championship information tells adult black belts to bring predominantly white and predominantly black rash guards for the later rounds.
So don't assume your limited-edition Satan Riding a Flaming Tiger Through Valhalla rash guard is competition legal because Satan appears to be wearing a purple belt.
Check first.
Different promotions can have different uniform rules.
8. Don't Confuse Expensive With Good
A €90 rash guard is not automatically three times better than a €30 rash guard.
Sometimes you're paying for better fabric, construction and design.
Sometimes you're paying because somebody put a skull on it and wrote WARRIOR MINDSET in Japanese.
And sometimes you're paying €90 for Japanese text that probably says municipal parking permit.
Focus on what you're actually getting:
Good compression fit
Stretch with solid recovery
Comfortable, durable seams
Enough length to stay put
Quality printing
Construction designed for grappling
A design you actually want to wear
Everything after that is preference.
If two rash guards tick those boxes and one costs significantly more, ask what the extra money is buying you.
If the answer is "premium warrior energy," put your wallet back in your pocket.
9. Yes, Design Matters
We can pretend this is entirely about performance.
It isn't.
You want to look cool.
That's fine.
Nobody buys a rash guard covered in Japanese demons because they carefully calculated the thermodynamic advantages of oni artwork.
Fightwear is part equipment, part personality.
Minimal black rash guard?
Clean. Serious. Possibly owns a spreadsheet.
Fluorescent psychedelic octopus strangling a Viking?
Excellent. No notes.
The best rash guard is ultimately one that performs properly and that you actually want to wear.
Because you're going to spend a lot of time in it.
Mostly underneath somebody.
Questioning your cardio.
How Many Rash Guards Do You Actually Need?
If you train once a week, one can technically work.
If you train regularly, buy several.
Not because Big Rash Guard has manipulated you.
Because you should wash your gear after every training session.
If you train four times per week and own one rash guard, you've created a laundry-based side quest that nobody asked for.
Two or three gives most recreational grapplers a reasonable rotation. Train almost every day and you'll probably want more.
And no, "I hung it over a chair overnight" does not count as washing it.
Your teammates know.
They have always known.
They discuss it when you leave.
The MF Rash Guard Checklist
Before buying, ask yourself:
Does it fit close without restricting movement? Good.
Is the fabric stretchy enough for grappling and built to recover its shape? Good.
Are the seams comfortable and constructed for repeated stress? Excellent.
Is it long enough to avoid migrating north every time you invert? Beautiful.
Are the graphics durable? Lovely.
Does it meet the rules if you're competing? Surprisingly responsible of you.
Does it look fucking awesome?
Now we're asking the important questions.
So, Which Rash Guard Should You Buy?
For BJJ, MMA and grappling, forget most of the marketing poetry.
Buy something snug, stretchy, durable, comfortable and built specifically for combat sports. Decide between long and short sleeves based on coverage and temperature. Check the seams. Check the size chart. If you're competing, check the rules.
Then choose the one that makes you look in the mirror and think:
Yeah. Tonight I'm definitely not getting submitted by Craig from Accounts.
You probably still are.
But you're going to look magnificent while he does it.
And that's where MF Fightwear comes in.
Our rash guards aren't designed for standing dramatically beside a squat rack while holding an energy drink. They're made for grappling—for rounds, scrambles, sweat, mat friction and the deeply personal humiliation of getting caught in the exact submission your coach demonstrated five minutes earlier.
Shop MF Fightwear Rash Guards → Collection
Pick your weapon.
Then go train.
Train hard. Wash your rash guard.