The 81C1A-E28-A13L is a 5/8" square single-turn panel control potentiometer manufactured by Bourns, designed for rotary switch applications with on-off function control. It features a metal shaft and bushing with consistent, smooth quality feel, and is available in up to 4 sections for flexible configuration. The device supports standard resistance ranges from 1 kO to 1 megohm with independent linearity of ±5% and an absolute minimum resistance of 2 ohms maximum, meeting RoHS compliance requirements. The potentiometer is commonly used in audio equipment, instrumentation panels, and control systems where reliable rotary switching and smooth operation are essential.