This band allows mounting of longer barrels on 1377, 1322, 1300KT and PC77 models. It's also a much more stable upgrade for the 2289G Backpacker. It's the Crosman Custom Shop 1300KT version. They are made of very stiff, durable polymer that is much harder, stronger and more stable than the older Backpacker version. The screw is steel, standard Phillips-drive size P2.
I have two versions of this band listed. The other is in the Custom & Upgrade Parts category. It's drilled and tapped to fit an included alloy-steel socket cap screw. It engages the full thickness of the threaded half of the band. I recommended that version if you plan to remove or adjust it regularly. It will withstand a lot more use and abuse without stripping the plastic threads.