The 91A1A-B28-B12L is a 5/8" square single-turn panel control potentiometer manufactured by Bourns with a plastic shaft and solder lug terminals. Based on the part number decoding, this unit features a 7/8" shaft length (code 28) with a 12-pin configuration (code B12L). The potentiometer is available in multiple element types (Conductive Plastic or Cermet) with resistance ranges from 100 ohms to 1 megohm, offering linear or audio taper options with tolerance specifications of ±5% to ±20% depending on the element type. The device provides virtually infinite electrical circuit isolation and is RoHS compliant, making it suitable for audio equipment, industrial control panels, and consumer electronics applications requiring reliable rotary control.