This is a very fine find, so we bought 'em all! Essentially, its a sturdy bracket with a ball bearing mounted shaft with dual timing belt pulleys. It consists of 1) 12 gauge (0.104") formed steel bracket 4-1/2" x 3-5/8" (Maximum LxW) with threaded inserts at all connection points and anti-corrosion plated (Cd ??), 2) a bearing/shaft assembly with a 0.318" diameter, 2.93" long shaft w/flats, two NSK 608D1 bearings, and a machined mounting housing, 3) two 25 tooth, 5 mm pitch timing belt pulleys, 4) a universal joint half (pin & block type), and 5) screws, spacers and roll pin for assembly. Unused. Sorry about the mixed fractional/metric measurements, but if NASA can do it, so can we!