Hey, if you've got a WERA Cyclop ratchet (you know, that cool round-headed ratchet), this socket is made specifically for it. It's a 3/8\ drive socket with a 12.0mm (that's about 0.47 inches) opposite hexagon opening. That means it's not your standard socket – the hex is on the *outside* of the socket head, designed to fit into tight spaces where a regular socket won't go. The total length is about 1.1 inches (29mm), and it's got a nice chrome-plated finish to resist corrosion. It weighs around 1 ounce (28 grams). This isn't part of a big set; it's a single, specific socket for that unique WERA ratchet system. Great for mechanics, DIYers, or anyone who loves having the right specialized tool for a tricky job. Just make sure you have the matching WERA Cyclop ratchet handle to use it with!