Airpel-AB driver's stainless-steel piston fits to the bore to create air bearing airflow effect. Four models with bores of 9.5, 16, 24, and 32.5 mm have strokes of 10 to 300 mm for pressures of 5 to 100 psi. Stiff air cushion prevents contact with cylinder wall by circumferentially supporting piston. Airpot Corp., (203) 846-2021, www.airpel.com