This is our standard 2X 1.25" Barlow lens with extreme broadband full multi-coatings and American machined parts. The black anodized insert tube has a safety groove and the black anodized eyepiece receptacle uses a brass compression ring. Stainless steel thumbscrew with knurled knob that is easier to control when using gloves. This is a great way to boost power while preserving the eye relief of your lower powered eyepieces. We did not include a filter thread on Stellarvue's Barlow's since it make much more sense to use the filter on the diagonal.