item #ProjLensNo2. This is a Bell and Howell (ADD ON LENS) projector zoom for 16mm projectors. The glass is clean and clear inside and out. The rear barrel has a diameter of 53.5mm with coarse threads cut into it. This lens will screw into a standard Bell and Howell 16mm projector lens and make it into a zoom. It will work with Lens No 1 listed on this page (a B&H 16mm Super D Proval 2" f1.4 Projector Lens). It may work with others also? Condition 10-.