This rack works great and is very well built. The rack grips my seat stem very securely. It can be moved if, for instance you kick it while mounting the bicycle, however, it certainly grips tightly enough to hold position during ride, even when fully loaded. Removing and re-installing pack is slick and convenient. Outstanding design. Make sure you order the proper rack type...the V Type worked great for my Cannondale T-1000. Unable to use fanny pack with this, however, not needed if you have a Topeak bag with side pockets. Further, if you ride without a bag, only using the rack as a fender, then a fanny pack would work fine.