
Boss O-Rings | McMaster-Carr
Ultra-Chemical-Resistant Kalrez 4079 O-Rings forTube Fittings with Straight-Thread Connection. Also known as Boss O- rings, these Kalrez 4079 O-rings are for use in tube fittings with a straight-thread connection. They’re inherently softer and more compressible than PTFE O-rings with comparable chemical resistance.