The SI Range of inch-size push-in fittings is offered for tube sizes 1/4 in OD to 3/8 in OD Superseal is a special fitting designed to provide extra grip on stainless steel tubes. The Superseal design features a collet with integrally molded stainless steel teeth similar to the standard Super Speedfit design, but incorporating an additional hand-operated nut and wedge shaped plastic washer to apply extra pressure to the collet and the double O-ring seals. This ensures that the collet teeth bite thoroughly into the tube to provide grip, while at the same time compressing the O-rings to further enhance sealing.