HEAT-TREATED ALUMINIUM ALLOY: High quality material and manufacturing process for extra strength and durability combined with low weight, WATER BOTTLES FIT: 26 OZ water bottle can fit snugly; min bottle diameter is 2.75inch(68.9mm) max bottle diameter is 3inch(76.2mm). The water bottle cage has arms (adjustable) that wrap around the bottle for a secure and firm hold so you don't have to worry about it falling out during your ride. EASY INSTALLATION: Use a 4mm hex key (included) to fasten cages in screw holes on frame. PLEASE NOTE - bike frame requires threaded holes for installation of cages. 2 SCREWS INCLUDED: The screws are standard size for water bottle mounts to most of bikes with DRILLED HOLES, and washers are suggested for tight fixing.