With a durable casing of flame resistant UL 94V0 plastic, the Pre-Wired 66Block With 1 Female RJ-21 Connector is the perfect choice for industries. This 66 block is simply pre-wired and is crafted for low voltage systems. This 66 block makes installation of a 25 pair amphenol telco cable simple. The brass is crafted of 100 micro inch of tin. Each terminal features gold over nickel plated copper alloy.