Potentiometer Rotating Switch Cap with Aluminum Alloy Knob Black 21*17*mm, External 15*17*mm, Inner Dia 6mm Name of Product: Customized Knob Size 6mm/1/4′′ is the standard bore size; however, it can be customized to meet your needs. Acceptable Materials: Brass/Bronze, Titanium, Aluminum 6061/6063/7075/2024, SUS 303/304/316, AISI 303/304/316L, etc. Depending on your needs, we accept finish machining, plain, polishing, zinc plating, black oxide, anodizing, passivation, galvanized nickel alloy plating, powder coating, etc. One potentiometer aluminum alloy knob (cap) is included in the packing service PET blister tray kit.