It is constructed of polycarbonate and is of professional quality. It has a knob for easy opening and closing. The lid snaps into place firmly. It can be used with all of the 5½" and 9” diameter bowls, including the white melamine, the black melamine, the stainless steel and the glass. These bowls are item numbers 44837-05, 44837-25, 44837B05, 44837B25, 42961-14, 42961-23, 41405-AA and 41400-AA.