Clothing rental services are giving fashion brands a hassle-free, no-risk platform to test an extended size range. As a result, more designers are flipping the switch to inclusive sizing.

On Monday, rental subscription service Gwynnie Bee launched an exclusive, size-inclusive collection by designer Shoshanna Gruss. The 12-piece collection, available in sizes XS to 5X and heavy in dresses, was inspired by best-selling pieces in Gruss’s 20-year-old contemporary line, Shoshanna, and designed to work on women of diverse sizes. For example, every style is bra-friendly.

Figure-flattering styles are a signature of Gruss’s, who first realized the void in fashion for curvy women when shopping as a busty teenager. In 2001, she became the first designer to sell bikini pieces as separates, allowing women to mix-and-match to fit their body type. Her core collection — sold in 400 retail outlets nationwide, including boutiques, department stores and Amazon — has been available in sizes 0 to 12 since launch.

“We’ve been talking about getting into this market for a while,” said Gruss, of plus-size fashion. “It’s always seemed like a natural fit, but it’s been hard for us to get into that world.”

The holdup, she said, has had to do with her wholesale-dependent business model and retailers’ hesitation to cater to the plus-size market. Some of her partner boutiques still only carry up to a size 8, and department stores’ rigid systems often leave young, plus-size shoppers high and dry: Extended sizes can be found in the women’s petites or plus-size departments, but not in contemporary.

There is a demand: Gruss said, for years, she’s been receiving emails and Instagram messages from women, questioning why she is not offering more sizes. Finally testing the waters, she said, took the partnership with Gwynnie Bee, which made the transition to more sizes easy.

“They already have a client base that trusts them, and I needed to work with someone who understood these sizes and had done the fittings, because I hadn’t,” she said. “It was a great learning experience for me to work with a company so well-versed in this.”

She said, rather than additional fit models and more patterns, which are often called out as hurdles by brands, the biggest expense most wholesale brands incur when launching extended sizes is hiring a separate sales team that understands the market.

It’s not the first time Gruss has worked with a subscription rental service; her brand, still carried by the company, was among the first available on Rent the Runway. One of the most valuable aspects of that partnership, she said, is the immediate feedback on styles from customers. She said she reads the online reviews regularly to see, for example, what fabrics women are liking and how they’re styling the pieces.

Shoshanna pieces are only available up to size 12 on RTR, but other featured brands are offered in a wider range of sizes. Rent the Runway currently has 160 styles available in its largest size of 22.

Anushka Salinas, Rent the Runway’s chief revenue officer, said the company’s merchandising team has worked with a large number of designers to make plus-size styles for the first time, resulting in incredible response and demand. Among them was Tanya Taylor, who used Rent the Runway as a test bed, later extending her main collection to size 22 across retail channels.

There’s much opportunity for brands in the underserved plus-size market. More than half of American women wear a size 14 or larger, and the plus-size fashion market is now valued at $21 billion.

Shoshanna dress, available at Gwynnie Bee

Gruss said, as with RTR, with her Gwynnie Bee collection, she is most excited to receive customer feedback, which she also gets from Instagram followers and store associates. Jessica Kahan Dvorett, vp of merchandising and brand for Gwynnie Bee, said the company shares with brands member preferences for colors, styles and design elements, as well as their feedback on the fit of each style. “This data helps us partner with designers and brands to make their collections more relevant and better-fitting each season,” she said.

Gruss said she and Gwynnie Bee are already working on a collection for next year and, because finding the right partner for launching a plus-size line was a long process, she’s planning to work with the company long-term.

Last year, Gwynnie Bee expanded its size range from plus-size-only to sizes 0 to 8. It now carries “hundreds of brands” in sizes 0 to 32, said Dvorett, who declined to share the company’s sales figures.  

To promote the Shoshanna collection at launch, Gwynnie Bee rolled out a social media campaign including an Instagram Stories takeover featuring models of diverse sizes, as well as fashion influencers. Members were notified of the launch in an email and able to immediately add styles to their cart. For her part, Gruss posted about the collection to her social channels, where she said she knows there are plus-size shoppers who have never been able to shop her collection.

She said, as fashion evolves and more shopping moves online, she expects making extended-size clothing will be easier.

“For now, we sell what stores want to carry and what their customers want,” she said. “But I’ve always been a student of fashion, and I’m always willing to try new things. My main goal is just to make women feel celebrated and loved and beautiful.”