Feature: 1. 1.25 INCH INTERFACE: The bottom extinction thread of this eyepiece can rotate a 1.25in filter and can be used with a standard 1.25 inch interface telescope or filter. 2. 4MM FOCAL LENGTH: The telescope eyepiece has a focal length of 4mm, with wide field of viewing, superior performance, very comfortable for observation. 3. MULTI LAYER COATING: The eyepiece adopts optical glass, FMC full multi layer broadband coating, providing maximum brightness and high definition. 4. METAL BODY: The body is made from premium aluminum alloy, which is sturdy and firm, not easily to break or damage. 5. WIDELY APPLICABLE: Used for astronomical observation of celestial bodies such as the lunar surface, planets, nebulae, star clusters, and diffuse nebulae. Specification: Item Type: Astronomy Telescope Eyepiece Material: Aluminum Alloy, Optical Glass Focal Length: Approx. 4mm/0.16in Interface Size: Approx. 31.7mm/1.25in. Package List: 1 x Astronomy Telescope Eyepiece1 x Storage Box