12 or 16 outer square edge suitable for sockets nominal size 12.5 (1/2"), 2 inner square adaptors for ratchets, sliding handles, extensions etc., A strong magnet securely holds the socket rail to ferrous metals, Additional holes are provided for wall mounting the socket rail or attaching to non-ferrous materials, The inserts are securely locked in place by the ball on the square by rotating them through 90B0., By turning 90B0 in the opposite direction the inserts are released and can be removed, Delivery without tools