Here is a completely unique, one-of-one Snap-On socket which has been misprinted. This ultra rare minting error is found on a new style Snap On 3/8 drive deep 17mm socket but has been printed as an 18mm socket. The Flank Drive Xtra socket comes lightly used (before realising the mistake) but is still less than 6 months old. Local snap on rep says he’s never seen anything like this before and has made an offer. Various photos show a 17mm Allen socket fitting perfectly inside the “18mm” Flank Drive Xtra alongside how loosely it fits alongside other Snap On 18mm sockets as normal.