.22 cal. Beautiful gun. This is my first Air Arms and they've done a nice job with this thing. Shoots with authority. Haven't done much sighting in aside from intial 10 yrds zero. Waiting on Neil's idc. But I can definitely tell you there aren't any flaws in its build. The bluing especially...almost see this rainbow effect in the metal that you see in puddles after it rains (shiny oily look). Shoulders sweet. Cycling is butter! The only issue that I have would be the marring of the end of the barrel from taking the muzzle break or ldc off and on again...