The VIM Tools6-pc 3/8" Drive Ratcheting Flare Nut Wrench Set, No. RFW100, includes a 10mm, 12mm, 13mm, 14mm, 17mm, and 19mm flare nut wrench head. Due to their shape and spring-loaded design, the set is compatible with both metric and standard sizes. The heads lock into the open position and snap closed once the user places it onto a fastener. As well as this, the heads have a closed end where the lips of the wrench overlap, allowing the head to fit against all sides of a fastener and hold tension.