Measure the diameter of your current bolt. If your bolt is 6mm in diameter you need the M6 Set. If your bolt is 8mm in diameter you need the M8 Set. Use a caliper or compare the bolt to a bolt with known diameter. Insert the Hexlox to block access to the bolt. The Hexlox Key "locks and unlocks" the bolt. Done!

Don’t forget that you need to protect both the saddle and the seat post. Even if the seat post is secured a thief could easily remove the saddle .