Isabel Rib Tank, BlackCitizens Of Humanity Isabel Rib Tank. The Isabel Tank is a modern essential, cut in ultra soft, supportive ribbed cotton with a close, flattering fit. Designed with a high neckline and clean finish, its ideal worn solo or layered under structured pieces. A polished base for elevated everyday styling.. This fit is true to size. Looks Like: Solid black tank Feels Like: Ultra soft organic cotton rib that holds the body 49% Tencel Lyocell 49% Organic