The Alpine Astronomical Baader 37mm Click-Lock Extension features a 37mm long 2" Click-Lock unit plus a 2" eyepiece barrel. Unscrewing the barrel reveals standard 2" Schmidt-Cassegrain telescope (SCT) visual back threads that allow it to be directly connected to the back of SCT optical tube assemblies for visual use with large eyepieces.

Unlike conventional compression ring and set screw holders, the unique Click-Lock system uses three long roller bearings to hold the eyepiece firmly centered in place without marking or marring it, while eliminating the wobble and off-axis tilt that is common with conventional holders. A simple 20° twist locks and unlocks the clamping system for fast eyepiece changes even while wearing gloves. Superior to conventional systems, there is no need to fumble with small set screws or for using excessive force and torque to hold the eyepiece in a fixed position.