This is a super-strong and ultra-light weight tactical round knob for any rifle or shotgun with a bolt or charging handle threaded for the common 5/16" x 24 TPI manufactured from genuine 3K carbon fiber composite (this is not some imitation stencil or printed film covering a plastic or aluminum knob). This is the same high-grade composite material used in expensive automotive parts, aerospace components and racing bikes.

Link to parts manufacturer