Piston installation is as important a procedure as any other during engine assembly. That is why Akerly & Childs Xtreme ring compressors are manufactured with the engine builder in mind. All compressors are machined with a step at the bottom to clear block o-rings when used. Xtreme compressors are manufactured from aircraft quality 6061T6 heat treated aluminum and then hard anodized for long life.Pit Stop USA offers Akerly-Childs 4.165" Xtreme Piston Ring Compressor AC-RC4165 at low everyday prices. Be sure to check out all of our products from Akerly & Childs including Akerly and Childs Engine Tools and Akerly and Childs Piston Ring Compressors.