Killer B Motorsport Type-R Shift Knob 6MT Subaru Models is NOT a Copolymer Shift Knob. Made from the superior material Delrin. Wonderful feel to this material, never too hot or too cold. The Delrin Shift Knob is strong enough to not require a brass insert to be used, which coincidentally the knob is stronger without an insert, and it holds a thread very well too. This simple design gives the best bang for the buck.