Abstract: A product and method of making a bellows from thermoplastic sheet material including forming a plurality of substantially U-shaped gussets having inside and outside edges, heat-sealing the inside edges of the gussets in pairs, heat-sealing the outside edges of adjacent pairs in an accordion-like stack, and then heat-sealing the stack of sealed gussets between a folded cover member of thermoplastic sheet material having an air passage through the cover member for communication with an expansible air chamber formed by the cover member and the gussets.