These split and hinged TMB optical tube mounting rings are made of solid aluminum, anodized black for long life. They are felt-lined and have a large hand-tighten knob to lock them on your optical tube. A heavy nylon washer prevents the knob from marring the anodized finish. The rings have a 142mm (5.6") internal diameter specifically to fit the TMB-130 refractor, but will also work with any other refractor having a 142mm OD tube. The rings weigh 25 oz. each.
There are five 1/4"-20 thread mounting holes on bottom of the rings for mounting on most equatorial mount dovetail plates. One hole is centered in the flat mounting boss in the bottom of each ring. It is flanked by a pair of holes on 60mm centers, and a second wider pair of holes on 80mm centers. An identical set of five holes on the top of each ring allow installing a second dovetail plate to carry accessories. Two 16mm (5/8") long x 1/4"-20 thread mounting hex head bolts are supplied with each ring for mounting the ring on a dovetail plate or equatorial mount using the center hole or either two of the two flanking holes.
