USG Corporation reduces installation time with its Durock Shower System by featuring pre-sloped foam shower trays. The fully-bonded waterproofing system for tiled shower installations is molded from 3-lb. density expanded polystyrene and includes a high-density polyethylene cross-laminated core for strength and tear resistance. Systems are available in three sizes: 48- by 48-in. center drain, 32- by 60-in. center drain and 32- by 60-in. offset drain.