D21A is a part of Legrand's range of wall mounted modular industrial switches and sockets. It is a 1-pole, 16A socket-outlet, which is typically used to provide electrical connections to machines, appliances, and other power and control devices. It features several safety features, including a double pole insulated shutter system to prevent accidental contact with live parts. The socket-outlet is also design certified to IP44 requirements, meaning it is splash-proof and protected against certain objects coming into contact with it.