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Two women in black one-piece swimsuits on a sandy beach by a white lifeguard stand; overlay: 'how we make decisions about our swim that fits like undies'

February 28, 2026

How We Decide What Sizes, Colors, and Styles to Make

TL;DR: We make decisions for our collection of swim that fits like undies based on real demand and customer feedback!

onewith is a swimwear brand offering XXS to 3XL swimsuits designed to fit like underwear.

If you’ve ever wondered:

This blog post is for you!

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Our Approach to Sizing

When we launched onewith back in 2021, our swimsuits that fit like undies were available in sizes XS to 3XL.

Based on customer requests, we quickly and thoughtfully expanded both ways and added XXS and 4XL, because we’ve always believed women shouldn’t need to change their bodies to feel their best in swimwear. (IYKYK: traditional swimsuits are the problem!). 

Over time, sales and return data showed two clear patterns:

  • XXS became a consistent seller for our dig-free swim

  • 4XL significantly underperformed (to the point where we barely sold any units), and most customers who did order a 4XL ended up exchanging for a 3XL beyond-seamless swimsuit.

Because we produce mindfully, every additional size increases development and production costs. (a little small-biz insider secret: it’s expensive to be a size-inclusive brand!) After reviewing demand and fit data, we made the decision to discontinue 4XL. This decision was not made lightly. To give you a peek behind the curtain…we actually lost money carrying size 4XL. A solid amount of money. It hurt our hearts to discontinue it, but the proof was in the pudding (data and sales). 

Size-inclusivity will always be at the center of our flattering swimsuit brand, and we will always offer sizes that truly fit and perform well across petite, midsize, and plus-size bodies, and we will continue, of course, to sell sizes XXS - 3XL. 

Why We Limit Colors and Styles

Another classic question we get all the time: “Why don’t you make more colors?!

Short answer? You guys tell us what you actually wear.

Since 2021, through countless prints, neons, and even classic colorways, one color has outsold everything: Abyss! Our black colorway just wins every. single. time. 

Launching every color in every style might look exciting, but for a small business, that can quickly become wasteful, so we test first.

For example, when we launched Jelly (the bright blue hue you’re obsessed with), we started with just two styles in our limited-edition Candycoated Capsule Collection. It quickly became a hit, so we slowly rolled it out across more of our raw-cut swimsuit silhouettes, and now it’s permanent in our collection of edgeless swimsuits!

We’d rather go deep on what works than wide on what doesn’t.

How Customers Shape What We Make

Customer feedback directly influences our decisions.

We review:

  • How quickly each of our better-than-seamless swim styles sell

  • Exchanges and returns

  • Comments, DMs, emails, and reviews

If you want new colors, styles, or expanded sizing, the biggest way to influence that is by shopping what’s currently available on our site!

FAQ

How do I know what swim that fits like undies size will fit me?

We offer XXS to 3XL and design our swimsuits to accommodate a wide range of body types and bust sizes.

Every product page includes a size quiz to help you choose the best fit. We also have a “See It On” section where you can view our swimsuits on customers, models, and influencers who share their measurements and the sizes they wear. 

If you are between sizes or unsure, our team is always happy to help you choose via DM or email!

Is onewith a size-inclusive swimwear brand?

Yes. Size inclusivity is and will always be central to our brand. We design our swimwear to flatter across petite, midsize, and plus size bodies within our XXS to 3XL range, and we continuously refine fit based on customer feedback.

Will you expand sizing or launch new colors in the future?

If consistent demand and fit data support expansion, we are always open to growing. We make those decisions based on sustainable production and long-term demand, not short-term trends.

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If you’re ready to find your fit, you can shop our full flattering swimsuit collection here. And if you want first access to new colors, restocks, and future launches, follow us on Instagram to keep up with all things onewith!

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