The Mallory MR21 Universal Flatted Shaft Volume Control is a replacement potentiometer component manufactured by P.R. Mallory & Co. for vintage electronic repair and radio restoration. Rated at 15K Ohms (15,000 Ω), this control features a base measuring 1-1/8 inches in full diameter and a 3-1/2 inch shaft length. The shaft configuration features a 3/4 round outer diameter with a 1/4 inch inner flat diameter for precise knob fitment and reliable resistance performance.