The 2" sleeve extension is a part to insert into a 2" eyepiece with a narrow range of motion to adjust the focus position. 35mm extension height CNC Cutting + Black Anodized for a Robust and Beautiful Finish The eyepiece adapter uses brass ring fastening system. Furthermore, the 2 fixing screws allow you to securely mount even heavy accessories. The 2" barrel has a straight type that does not snag when putting on or taking off. Of course, the barrel tip is also equipped with a 48mm filter thread. Carefully inner treatment prevents reflection stray light, and can be used with peace of mind for moon and planetary observations where contrast is important.