Celestron Dielectric Star Diagonal, 2” with Twist-Lock

General Diagonal size: 50.8mm (2") Diagonal type: Mirror Glass material: BK7 Coatings: Dielectric, 58 layers Reflectivity: Over 99% Optical quality: Diffraction limited Eyepiece holder: 2", Twist-Lock 2"-to 1.25" Stepdown adapter: Included, Twist-Lock Compression ring: Yes, dual rings for a 2" eyepiece holder and a single ring for a 1.25" step-down adapter Housing construction: Machined aluminum black anodized Barrels: Comes with 2" barrel (for connection to 2" focusers) and SCT adapter (for connection to SCTs) Barrel interior: Glare threaded and painted flat black Threads for filters: 2" barrel and 1.25" step-down adapter have 2" filter threads Dimensions: 152.4mm x 76.2mm x 101.6mm (6" x 3" x 4") Weight: 19 oz (538.6 g) (with step-down adapter)