This is a kit of 66 punch-down block and mounting bracket in one box. A 66 block is a type of punch-down block used to connect sets of wires in a telephone system. The A blocks have 25 slotted holes on the left side for position the incoming building cable with a 50 slot fanning strip on the right side for distribution cables. 66 blocks are designed to terminate 20 through 26AWG insulated solid copper wire or 18 & 19 gauge skinned solid copper wire.