About the Full Tilt (now K2) FTE Pro Tongue Flex 12
Full Tilt's replacement tongue with a flex of 12, equivalent to a flex rating of 130. This tongue is compatible with any Full Tilt boot with an Evolution shell.
To identify the shell of your Full Tilt boot all you need to do is count the number of screws on the bottom of your boot. Full Tilt boots with an Evolution shell have 8 screws holding the sole in.