Keystone Electronics Corp. Polarizing Washer-Red 59

Part number 59 is a red polarizing washer made of molded polyethylene, designed for use with AA, C, and D cell batteries to prevent improper battery installation by ensuring only the positive dimpled contact makes contact. It features a pressure-sensitive adhesive back that adheres to all surfaces without gluing or wetting, and its red color provides intuitive polarity indication. The washer has a diameter of 1.375 inches [34.9 mm] and a thickness of 0.250 inches [6.4 mm].