The 2890AC is a black phenolic knob designed for manual control and adjustment in electronic and mechanical equipment. It features a concentric circle pattern with matte finish and heavy straight knurls for improved grip and tactile feedback. The knob has a main body diameter of 2.5 inches (63.50 mm) with a 1.260 inch diameter shaft interface, and includes a 1/2-13 UNC-2A threaded insert (steel, zinc-plated) for secure mounting. The design incorporates a 1/4 inch (31.75 mm) height with a 27/32 inch (21.43 mm) landing bar and radius details for ergonomic handling. This knob is commonly used in control panels, test equipment, and industrial machinery where reliable manual operation and durability are required.