WunderUndies
Kids Briefs - Flat Seams
Kids Briefs - Flat Seams
Build a Pack
$9 - $13
It is highly recommended that if you are new, you first purchase the Find My Size Trial Pack to test for sizing and comfort as WunderUndies are non-returnable and non-refundable.
Couldn't load pickup availability
PRODUCT DESCRIPTION
PRODUCT DESCRIPTION
Say hello to our latest innovation in sensory-friendly comfort: WunderUndies briefs with flat seams. Thoughtfully designed to meet the needs of kids with sensory sensitivities, these briefs take our commitment to comfort and inclusion to the next level.
What sets these apart? Our new construction eliminates bulky inside seams altogether, ensuring a smooth, irritation-free fit. While our previous designs already prioritized softness and comfort, we’ve listened to feedback from parents and kids alike to create an option that feels like a second skin—perfect for those who need an extra touch of sensory ease.
Crafted from our signature bamboo fabric, WunderUndies are not only buttery-soft but also breathable and eco-friendly. They feature our same fun, gender-inclusive designs that kids love, making them a favorite for self-expression. Plus, the flat-seam design means no tags, no bumps, and no distractions—just pure comfort for play, rest, and everything in between.
At WunderUndies, we’re always striving to evolve, and this new flat seam style is a reflection of that growth. Whether your child is already a fan of our original WunderUndies or you’re discovering us for the first time, we’re confident these briefs will become a staple in their wardrobe.
Give your child the gift of ultimate comfort and confidence with WunderUndies Flat Seams Briefs. Because every kid deserves to feel good in their own skin—inside and out.
WASHING INSTRUCTIONS
WASHING INSTRUCTIONS
Some people see bamboo fabric and worry that it will be hard to care for. It's not! Many customers have praised the durability of WunderUndies. Here's what you need to know:
Machine wash cold with mild detergent. No fabric softener. Dry on low. If you feel the need to iron your undies, do that on low too. These are the practices for the longest lasting undies.
OUR BAMBOO COTTON BLEND
OUR BAMBOO COTTON BLEND
Our fabric blend of 67% bamboo, 28% cotton, and 5% spandex is crafted to provide unmatched comfort, durability, and versatility. Bamboo offers exceptional softness, breathability, and moisture-wicking properties, making it perfect for sensitive skin and active kids. Cotton adds strength and structure, ensuring long-lasting wear, while the addition of spandex delivers just the right amount of stretch for a snug, flexible fit. This thoughtful combination creates underwear that feels gentle, moves effortlessly, and stands up to everyday play, all while supporting sensory-friendly comfort.
SOFT VS FLAT SEAM BOXER SIZE
SOFT VS FLAT SEAM BOXER SIZE
With WunderUndies first round of boxers, it quickly became clear that they ran small. So with the next round we made some needed changes. They are:
1. We shifted everything one size. Our old size 12s are now size 10s and so on and so forth.
2. We enlarged the waistbands ever so slightly.
If you have bought from us before and are worried about what size might fit your child now, you are welcome to get another trial pack. But if you are new to WunderUndies we believe that the size chart above now more accurately reflects the best fit for our Flat Seam undies. If you are buying Soft Seam Undies, consider sizing up.
As always, we highly recommend getting a trial pack first.
Size Chart
 |
|
The waistband on WunderUndies is very snug. If your child doesn't like snug clothing, consider sizing up.
Let customers speak for us
from 12 reviewsWe got a trial pair for our kiddo and had to come back and get a bunch more! Kiddo is girl-identifying, born with a vulva, and prefers to wear "boy" briefs due to sensory needs but sometimes had issues with underwear gaps when sitting down wearing a dress. She LOVES the trial pair and says they are more comfortable than any other undies she's ever worn! She likes the feel of the fabric ("girl" undies fabric feels too thin and "boy" undies just aren't as soft) and prefers the waist and leg bands to the elastic on "regular" undies. She also likes the patterns but would probably wear them even if the prints were boring because they are so well designed.
As a mom of a 6yo boy who is usually only in shorts bc underwear are hard to find that meet his requirements. He loved them, took him a bit to actually put them on but when he did he was surprised at the softness and how they fit. He is also very active and they stayed in place. Not to mention he wore them to his MRI and the Dr. and nurses were just as impressed with them.
Only downside for us is the price as a special needs mom we can not afford to have many of them, although we completely understand your time and the cost of materials ect. We thank you for making wunderundies, sensory-friendly for families like our!
My daughter has a sensory issue with underwear and these panties (two different styles) have been amazing! No more digging in her underwear! THANK YOU!
My daughter absolutely loves her new Wunder Undies! No elastic that digs in and she loves to pick out the design each day. I would love to see some neutral solids like nude or tan to wear under white and light colored clothing.
My girls (7 and 9) both adore these briefs and complain to me if we don't have any wunderundies in the clean laundry. They are very fussy about underwear and these are the clear winners. They are also sturdy and are holding up great to frequent washing.
My daughter was hooked after we got our 1st pair. She loved how comfortable and fun they were. And I loved that they were good coverage appropriate for her age. Not those teeny bikinis that are in stores for size 6 kids!. Win/win!
My son and daughter both LOVE these undies. The fabric is super soft, and the kids were obsessed with the adorable prints!! 100% recommend especially if your kiddos have sensory sensitivities!
Had to grab more of these WunderUndies after my boys fell in love with their first pairs and were always asking for their ice cream and donut undies! My oldest struggles with tags (we’re always cutting them out), so tagless undies are a must for us. They're also super soft, which is another win for sensory sensitivities. Even my little one, who's in the 'No get dressed' phase these days, loves picking out his undies each day. Those fun prints make all the difference! We love our WunderUndies and will definitely be back for more. 💜