Topeak Fuel Tank Top Tube Bag: Medium Black. A medium capacity top tube mounted bag giving a cyclist quick and easy access to essential gear.Straps securely to the top tube and head tubeZippered main compartment also has a flap to keep contents safe and secureMaterial: 420 Denier Nylon / PVC SpongeTop Tube Diameter Fits: 38 – 52mmHead Tube Diameter Fits: 34 – 75mm