Twist-Up eyecups SV191 7.2-21.6mm zoom eyepiece can meet the needs of most people; including the needs of users who wear glasses. Fully Multi-coated lens SV191 zoom lens optic design increases light transmission, delivers bright, clear, high-contrast images even in low-light conditions. Specification: Focal Length: 7.2-21.6mm Eye Relief: 18-20mm Apparent Field of View: 42°-65° Field stop diameter: 16mm Barrel Size: 1.25" Lens Structure: 7-Elements/4-Groups Filter Threads Standard: M28.5*0.6 Coatings: Fully Multi-Coated Blackened Lens Edges: Yes Eyecups: Twist-Up Eyecups Material: Metal Net Weight: 167g / 5.87oz / 0.367lb Package Includes: 1X Black 1.25" Zoom Eyepiece 7.2-21.6mm 2X Rubber Dust Cover 1X Mirror Cloth. Features --Dielectric coatings provides 99% reflectivity --M28.5x0.6 filter thread can connect with 1.25in filter directly --Built-in brass ring to prevent the accessories barrel from being scratched --Machined and anodized aluminum housing make the SV188P dielectric diagonal durable and uniform. Compatible with Telescope.1.SV188P 1.25in dielectric diagonal compatible with any 1.25in refractor telescope . 2.SV188P can not connect with the SCT telescope directly, the additional adapter is required if you want to connect SV188P with the SCT telescope. 3.SV188P does not fit for reflector telescope. Specifications: Size: 1.25in. Coatings: Dielectric. Reflectivity: 99%. Thread: 28.5*0.6. Material: Aluminum Alloy. Screw: M4 Set Screw. Net Weight: 125g / 4.41oz. Package Includes: 1 x 1.25in 90 Deg Dielectric Mirror Diagonal, 1x M4 Screws,1x Dust proof plug,1x Dust proof cover.