Isabel Marant Billy Underwear in White. - size XS (also in ) Isabel Marant Billy Underwear in White. - size XS (also in ) 94% cotton 6% elastane. Made in France. Machine wash. Pull-on styling. IMAR-WI1. SL0012HA-A3I15H. The pioneer spirit - During the brand's early days, a unique silhouette is born: the contemporary Parisian girl. Products that became iconic, simple yet effective. The brand is ahead of its time, with an outsider state of mind, always a bit off the road. Shop the latest in fashion from Isabel Marant