Item Type: 1.25 Inch Mount to C CS Mount Adapter Material: Aluminum Alloy External Thread Specification: M25x0.75mm (Commonly Known As: C Port/CS Port Thread) External Thread Depth: Approx. 5mm / 0.2in Internal Thread Specification: M28.6x0.6mm Internal Thread Depth: 4mm / 0.16in Outer Diameter of Mount: Approx. 1.25 Inches (31.6mm0.1mm) Overall Length: Approx. 30mm / 1.2in Color: As Pictures Shown Weight: Approx. 16g / 0.6oz Package List 1 x Adapter 1Scope of Application: 1.25 inch to C CS mount adapter fits any telescope C mount (male thread) telescope eyepiece changer with a 1.25 inch eyepiece tube. 21.25 Inch Mount and M25 Thread: The 1.25 inch mount is suitable for filters, focus reducers, and extenders. M25 external thread is suitable for C mount or CS mount camera lenses. 3Aluminum Alloy Material: Made of black anodized aluminum alloy, which is wear resistant, durable. The adapter is fully threaded inside to minimize reflections of stray light. 4Internal and External Thread Specification: External thread specification is M25x0.75mm (commonly known as C mount, CS mount thread). Internal thread specification is M28.6x0.6mm. 5Adapter Size: External thread depth is 5mm / 0.2in, internal thread depth is 4mm / 0.16in, outer diameter of mount is about 1.25 Inches (31.6mm0.1mm), overall length is 30mm / 1.2in.