This is a very nice Bausch & Lomb lens assembly made of Brass and painted black. Front lens has a clear diameter of 15mm and the rear lens has a clear diameter of 8mm. This assembly has a 25mm focal length and is multi-coated. The housing is 70mm long by 25mm in diameter which tapers down to 20.5mm at the rear where the threading starts. The threaded area is about 13mm wide. At the front of the lens there is internal threading that has a diameter of 19mm. Engraved in the housing is # 007-4097001.