Seamless Cotton Underwire Cups, cup extensions, center: 92% Cotton, 8% Spandex. Center lining, cup extension lining: 100% Nylon. Back: 95% Cotton, 5% Spandex. Exclusive of other trim and elastics. Hook and Eye closure Seamless two-ply stretch cotton cups look smooth under clothes. Full coverage with open neckline design. Soothing Stay put design with No-Slip straps. The perfect T-shirt bra --shapes you smoothly under clingy knits.