J. Crew Group, while continuing to rework its J. Crew collection, appears to be evolving its selection of third-party brands to fill voids in the assortment and test new products and fabrics. J. Crew won’t comment on its third-party strategy, but the latest edition was Tuesday with the introduction of Mack Weldon for J. Crew Prime Cotton men’s underwear. Previously, Mack Weldon sold its core underwear range to select J. Crew stores. Prime Cotton marks the first time Mack Weldon designed exclusive product for the retailer. The products — boxer briefs priced $28; button-fly boxers, $32; trunks, $24, and undershirts, $38 — are sold on jcrew.com and at 19 J. Crew stores. Other third-party brands on the web site include Lacoste, Vans, Sperry, Alden and Le Specs, an Australian sunglasses firm.

Mack Weldon for J. Crew Prime Cotton men’s underwear. 

J. Crew’s web site describes Prime Cotton as “a rib-knit fabric developed exclusively with Mack Weldon. It combines durable long-staple cotton with climate-regulating nylon for a fabric that’s stronger and cooler than regular cotton.” Michael Isaacman, cofounder of Mack Weldon, said: “J. Crew’s innovative men’s shops, coupled with their unique ability to curate third-party brands alongside their own product, made this an ideal match.”

J. Crew, still in turnaround mode, is striving to be younger in appeal and more accessible with prices and fits. It’s also creating subbrands and emphasizing its iconic items like rugby shirts and roll-neck sweaters. A relaunch” of the J. Crew brand is planned for September, but next year, greater change will be evident since J. Crew just hired a new creative director, Johanna Uurasjarvi.