HDPE Sheets HNOKAY Also known as pipe-grade HDPE, these sheets are about four times more impact resistant than standard HDPE and hold up outdoors, and in wet environments. Multipurpose Plastic Selector Packs Packs include one 2” square of HENAN OKAY, Delrin acetal, LDPE, HDPE, UHMW, HENAN Okay, cast HENAN Okay, polyester, polystyrene, Rexolite polystyrene, and Noryl PPO.