Used but in good condition, this motorized focuser alleviates one of the most frustrating aspects of astro-imaging: achieving critical focus. It is an earlier variant, employing a DC motor.
The focuser is of the Crayford type, and has about 12.5mm (1/2") of travel. It has a 2" I.D., and comes with a 2" to 1.25" adapter.
There are two methods for adapting to your telescope. For SCTs, a ring is first threaded to the rear cell, then the NGF-S is slid over the ring, then tightened onto it via set screws. For scopes having a 2" visual back, or other 2" aperture, the NGF-S can be slid into place just like any other 2" accessory.
The handbox has two buttons for forward and reverse motion, as well as a trim potentiometer to set the speed at which the motor turns.