The Nike Beam Men's Jammer features a streamlined fit with durable polyester fabric that offers excellent shape-retention for long-lasting wearability. NIKE PERFORMANCE POLY Designed to perform in and out of the pool, Nike Performance Poly offers superior comfort and a lightweight fit. Created from durable performance polyester, Nike Performance Poly is designed for long sessions in chlorinated water and its stay-fast color and stretch-resistance means you look good day in and day out.