Snapbloc Power Distribution Block, Modular Design, Mechanical connection, Dual Rated, Aluminum material, Tin plated connector,mounting bolt/stud size 1/4 in, mounting hole spacing 4.75 in., UL 1059 Recognized, C22.2 No. 65-03, Copper/Aluminum Primary Conductor 500 kcmil - 4 Str, Copper/Aluminum Secondary Conductor 500 kcmil - 4 Str, 2 conductors, 2 ports/wireways, Drive Type Main 3/8 Internal Hex, Drive Type Tap 3/8 Internal Hex, rated for 600 V, primary color Blue, 1 poles, 1 ports per pole primary, 1 ports per pole secondary,