Abstract: An inflatable bladder is defined by two superimposed outer sheets of heat-sealable synthetic plastic fused together about their peripheral edges. An Intermediate layer or baffle is disposed between the two outer sheets and is alternately sealed to one and the other of the outer sheets to form air cells on the opposite sides of the intermediate layer. Each of the air cells is defined by an opposed surfaces on one side of the intermediate layer and of one of the outer sheets and adjacent seals which fuse together the layer and each sheet. The seals which define the cells on one outer surface of the bladder are offset from the seals which define the cells on the other surface of the bladder. Opposite surface portions of the intermediate layer are coated with a barrier layer to prevent heat-sealing on each side of the intermediate layer opposite the seals on the other side which form the cells whereby the bladder and the cells thereof may all be formed simultaneously in one heat-sealing operation.