Metal Body, • 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