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).