SilencerCo AC28 Osprey/Octane piston designed for SilencerCo Osprey and Octane suppressors. Made from 17-4 stainless steel, it features a 16mm x 1 Left Hand thread pattern and is compatible with .45 Auto caliber handguns. MPN AC28, UPC 817272010183. Not available for shipping to California, Illinois, Massachusetts, or Washington. Brand: SilencerCo.