100KA Short Circuit Current Rated Power Distribution Block. 2 X 500 MCM-4 Awg Line, 2 X 500 MCM-4 Awg Load Power Distribution Blocks Are Made Of Valox Nylon 6/6, Finger Safe Lexan 500R Polycarbonate Panels and Covers, High-Conductivity 6061-T6 Electro-Tin Plated Aluminum Alloy Connector. Each Block Can Stand Alone or Combine With Other Blocks to Form A Multi-Block Set, and Are Also Din Rail Mountable With Built In Locking Mechanism to Lock/Release.