The Boyshorts are soft, stretchy, and reduce friction between your thighs.
Customer Reviews
2,836+ Women Can’t Be Wrong
4.8
★★★★★
Verified Purchase
“I’ve been searching for underwear that smooths without squeezing for years. This is it. The waistband sits perfectly, no rolling, no digging. I wear them every day and I’ve ordered six more pairs in different colors.”
★★★★★
Verified Purchase
“These are the most comfortable underwear I’ve ever owned. They’re not shapewear — they just make everything look smoother. I wore them under a fitted dress to a wedding and got so many compliments on how I looked.”
★★★★★
Verified Purchase
“I bought these with the matching bra and it’s the best set I’ve ever owned. The brief smooths my waist beautifully and I forget I’m wearing them. The 180-day guarantee meant I had nothing to lose trying them. Now I’m a customer for life.”
Join over 1 million women who have already made the switch.
Shop the 308 Smoothing Brief
30+
Years of
Lingerie
Expertise
Lingerie
Expertise
Why Underoutfit
Smoothing that disappears under everything
Our founders spent 30+ years designing for Victoria’s Secret, Nike, Spanx, Lululemon, Triumph, Maidenform and more. They built the 308 Brief to solve what no other underwear had — a waistband that smooths without digging, shapes without compressing, and disappears under any outfit.
Smoothing Waistband — No Digging
Engineered to smooth and contour at the waist without any pressure, rolling, or digging into the skin — even after a full day of wear.
Seamless Under Any Outfit
Ultra-thin seamless construction lies completely flat under fitted dresses, trousers, and activewear — invisible from every angle.
All-Day Comfort, Every Day
Soft, breathable fabric moves with your body from morning to night. Not shapewear — just underwear that happens to smooth beautifully.
180-Day Risk-Free Trial
Wear it, wash it, try it again. Return or exchange free for 180 days — we pay the shipping both ways.
Engineered for Comfort
Every Detail, Designed with Intention
Three decades of intimate apparel expertise went into every stitch. Here’s what makes the 308 Smoothing Brief different from anything you’ve worn before.
01
The Mechanism
The Waistband That Holds Without Marking
Most waistbands do one of two things: dig in and leave marks, or sit loose and do nothing. Ours does neither.
The 2-ply waistband is engineered at the yarn level — not compressed onto your body, but knitted to sit flat and hold. No elastic bands. No hard edges. No red marks when you undress.
2-ply construction — double layer at the waist gives smooth, even hold without a single pressure point
No hardware — zero elastic, wire, or rigid bands to cut in throughout the day
Tubular knit technology — the waistband isn’t sewn on. It’s knitted as one continuous piece, so it can’t roll or bunch
02
The Fabric
Second-Skin Feel. All-Day Breathability.
We don’t call this shapewear. That’s not an accident — traditional shapewear compresses. This fabric holds its shape around you, not against you.
The result is something most women describe the same way: you forget you’re wearing it. Your waist doesn’t.
No visible panty line — seamless finish sits flat under any outfit
Moisture-wicking — cooling fabric treatment keeps you fresh from morning to evening
Level 1 shaping — enough to smooth, never enough to restrict. Not for special occasions. For every day.
03
The Fit
Seamless Silhouette
No raised seams, no visible lines, no panty outline under clothes. The 308 disappears under everything — fitted dresses, tailored trousers, lightweight fabrics. You'll forget you're wearing it. Your clothes won't show that you are.
Runs true to size — if between sizes, size down for a smoother hold
Available S through 3X — inclusive sizing with the same fit experience across the range
308 Smoothing Brief
Built for Every Day —
Not Just the Days
That Need Shapewear
Most smoothing underwear is occasion-wear. You pull it out for events. You suffer through it. You take it off the moment you get home and swear you'll find something better.
The 308 Brief was designed for Tuesday. For the commute, the desk, the school pickup, the errand run, the dinner out. Wear it every day — wash it every night — and it holds its shape, wash after wash.
Monday
The commute.
7am to 10pm.
Tuesday
Back-to-back
meetings.
Wednesday
The errand run.
No adjusting.
Thursday
Dinner out.
Forgot it was on.
Friday
The long day.
Still there at 10pm.
20+ Colors
Match your undertones, coordinate your wardrobe, or just pick the one that makes you smile. Same fit experience across every color.
"S" Through "3X"
SmoothKnit fabric stretches more than it looks. Order your regular size. Unsure? Order two — return one free, no questions asked.
Wash After Wash
Same structure on wash 1 as wash 100. No elastic degradation. No shape loss over time. Machine washable.
Underwear you forget you own. That's the whole point. Not shapewear you endure — underwear that works so quietly you stop thinking about it entirely.
180-Day Trial↩
We let you wear it,
wash it, and still return it.
We offer a 180-day free return and exchange policy. Not because we have to — because we know what happens once you actually feel the difference.
Wear it. Wash it. Live in it. If it's not the most comfortable underwear you've ever owned after 180 days, we'll take it back. No questions, no restocking fees.
We can afford to do this because the return rate is low. Women don't send these back.
180
Days to try at home. Worn and washed.
Free
Returns and exchanges. No questions asked.
4.8★
Average across 2,698 verified reviews.
FAQS
Questions? Start Here.
Everything shoppers usually want to know before trying the 308 Smoothing Brief at home.
180-day fit promise
Try it, wash it, wear it again. Free returns and exchanges if it is not the one.
What makes the SmoothKnit System™ different?
Most smoothing underwear blends spandex into a single layer of fabric — and that spandex is what breaks down fastest, typically within 3–6 months of regular washing. The SmoothKnit System uses a 2-ply knitted construction where the smoothing comes from the structure of the knit itself, not from spandex tension. That structure doesn't degrade the same way. Same shape, same smoothing on wash 100 as wash 1.
How does it smooth without feeling like shapewear?
Traditional shapewear compresses. The 308 Brief supports. The high-waist design and 2-ply knit create a smooth silhouette at the waist without squeezing or restricting movement. You can wear it all day — through meetings, errands, evenings out — and forget it's there.
What size should I order?
SmoothKnit fabric stretches more than it looks. Order your regular size. Unsure? Order two — return the one that doesn't fit for free. We cover the shipping both ways, so there's no risk in trying.
Will it show lines under clothing?
No. The seamless construction and smooth-edge waistband are designed to disappear under everything — fitted dresses, tailored trousers, activewear. No lines, no bulk, no visible waistband ridge.
Does the waistband roll or dig in?
The 2-ply waistband is engineered at the yarn level — knitted to sit flat and hold, not compressed onto your body. No elastic bands. No hard edges. No red marks when you undress. Customers consistently report the waistband stays exactly where it starts, from morning to night.
What is the 180-Day Try-at-Home policy?
We offer 180 days for returns or exchanges. Wear it, wash it, try it for real. If it's not the most comfortable underwear you've ever owned, send it back. We pay the shipping both ways, no questions asked.
What is the fabric and how do I care for it?
The 308 Brief is made from 92% Nylon / 8% Spandex. Machine wash cold. Do not use fabric softeners — they coat the fibers and reduce breathability. Use non-chlorine bleach only if needed. Tumble dry low or line dry to preserve the SmoothKnit structure.
How many colors are available?
The 308 Brief is available in over 20 shades — from neutrals like Sand, Black, and Navy to seasonal colors like Sapphire, Fuchsia, and Pale Lilac. Whether you're matching your undertones or coordinating with your wardrobe, there's a shade for every mood.
Press & Media
As Seen In
So comfy you forget you’re wearing them.
The Bra is a feminine, comfortable bra that enhances your natural shape.
So many reviewers are calling it their “new favorite bra.”
Very few brands offer such a long period for returns or exchanges.
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Our Story
Designed by the people who built the industry
Our founders spent 30+ years designing bras for Victoria’s Secret, Nike, Spanx, Lululemon, Triumph, Maidenform and more. They know what works — and they know what women actually want. Now they’re bringing that expertise directly to you.
Expert Craftsmanship
Every bra is the result of decades of intimate apparel engineering. Perfected fit for millions of women worldwide.
Women-First Design
Every detail is made for real bodies and real life. We design for how women actually live — not how they’re supposed to.
Trusted by 2M+ Women
Over one million customers have made Underoutfit their everyday essential. Join a community that knows what comfort really means.
“A bra to forget. — that’s not a tagline. It’s the standard we hold ourselves to every single day.”
Our Promise to You
180 Days to Fall in Love
We’re so confident you’ll love our garments that we give you 180 days to decide. Wear it, wash it, try it again. If it’s not right, return or exchange it — completely free.
- 1 Order your size — or try two sizes at once
- 2 Wear it, wash it, wear it again
- 3 Not right? Return or exchange — free, for 180 days
180
Days Try at Home
Wash & Wear · Free Returns · Free Exchanges