All our other accessories -1.25'' Collimation Eyepiece for Astronomical Refractive Telescope Highlights generic brand 1.25'' Collimation Eyepiece for Astronomical Refractive Telescope Description: The 1.25 inch calibration eyepiece is of short size, made of aluminum alloy. Used to calibrate the optical axis of a refractor, place the collimating eyepiece into the tube. Make sure the black spot is in the center of 2 collimation eyepiece lines. Please adjust the screw if it is not in the center, in this way you collimate successfully. A wonderful accessory for photography and astronomy enthusiasts. Specification: Material: Aluminum Alloy Color: Black Caliber Diameter: 1.25 inch Suitable for Refracting Telescope Length: Approx. 64mm / 2.52inch Diameter: Approx. 35 mm / 1.38 inch Package includes: 1 Piece Short Collimation Eyepiece