These are hand made bolt action knobs. They are made from a variety of materials such as G10, linen and canvas micarta, burlwoods, and "resinwoods? Any of the layered materials have a brass threaded insert for strength (or any material that needs the added strength).
Most of the knobs are available with a case head inserted into the top, and unless otherwise noted, you can choose what caliber. Most are threaded 5/16-24 (so of course require a threaded bolt handle), but if you have a rifle with a unique thread or layout like the Desert Techs, please contact us with your requirement.