The topeak dual side frame is designed for use with the topeak mtx beam rack or the topeak mtx ex beam rack to make them suitable for use with pannier bags to stop the sides of the bag from hitting your wheel the pannier frame fits easily and securely onto the pannier rack in a matter of seconds and is just as easy to remove if necessary specifications of the topeak mtx dual side frame size 294cm x 2cm x 304cm l x w x h weight 300g compatible with topeak mtx beam rack