Revelate Designs Mag Tank Top Tube Bag - Black Bolt-OnMag Tank Bolt On Stem Bag: The Mag Tank takes a new twist on top tube bags. Instead of a zippered opening, access to the bag is by contoured top flap held in place by a magnetic buckle with mechanical engagement. It will not unintentionally open and spill your gear. Grommeted holes in the bottom of the bag allow it to be bolted securely to the top tube of frames with the provided mounts, and a stem strap provides additional stability. Magnetic buckle