Membran

Diaphragm: The Rolling Diaphragm is a tough,flexible seal with a unique configuration that permits relatively long piston strokes while completely eliminating sliding friction.Formed in the shape of a truncated cone, or top hat, the diaphragm is turned in on itself when installed so that, during the stroke, it rolls and unrolls alternately on position skirt and cylinder wall. The rolling action is smooth and effortless, completely eliminatinf sliding contact and breakaway friction