Solomark Chesire Collimating Eyepiece Metal Body with Crosshair 1.25 Inch Fitting Short Special eyepiece fits into 11/4" focusers or diagonals. For aligning optics of Newtonian reflectors, Dobsonian reflectors, and Schmidt-Cassegrain Telescopes (SCTs) Collimation eyepiece is more accurate than the simple Collimation Tool When collimating a refractor you should put the Cheshire directly into the focuser. With Dustproof and MoistProof Rubber Cover-Expert Design-CNC Machine Made- Precise Surface Dealing