The finest single-viewing-pupil autocollimator money can buy!
Jim Fly's Catseye 2" Infinity XL Autocollimator is considered to be the BEST single-viewing-pupil autocollimator available, and features a premium, optically flat first-surface mirror, with 97% reflectivity and dielectric-coating for protection. Precise mirror registration ensures perfect internal collimation. Inferior copycat products typically have a lower quality mirror poorly aligned within the tube.
Not all telescope Autocollimators are equal
Supplied with full instructions.
Note: An autocollimator compliments a traditional Cheshire/Sight-Tube, it doesn't replace it. The Cheshire/Sight-Tube is still the best tool for positioning the secondary mirror under the focuser.