The L21CH20 is an illuminated stay-put pushbutton head designed for control and signaling applications in industrial environments. It features a 22 mm diameter flush design with a plastic chrome bezel and is available in red, green, yellow, white, and blue LED options. The unit conforms to IEC 60947-5-1 standards and provides IP 66 to IP 69K degree of protection, making it suitable for harsh operating conditions. It is equipped with a locking ring and is designed to be combined with a clip, LED block, and contact blocks for complete assembly. Common applications include machine control panels, emergency stop systems, and industrial automation where visual feedback and maintained contact operation are required.