Are made of two plastic laminate (plastic laminate design will vary from one to the other) covered particle boards with s stainless steel ball bearing, screwed into the inside surfaces of the boards. The 8" & 10" turntables have a 4" bearing capable of supporting at least 200# and the 12", 14" & 16" have a 6" bearing capable of supporting at least 300#. To clean, wipe with a damp sponge (do not submerge the turntable in water).