Mag Tank Bolt-On (TPU Liner)Description Revelate Designs took the beloved Mag Tank and made a version compatible with top tube bolt bosses. The Mag Tank takes a new twist on top tube bike bags by doing away with a zipper! The Mag Tank features a smartly contoured top flap secured by a magnetic buckle with mechanical engagement, ensuring no accidental openings, even when your bike is upside down. With one handed operation, simply pull the cord loop outward for full top access;