The Fastfuel Bag Essential by Topeak is a compact and aerodynamic top tube fuel box that minimizes wind resistance. It has a secure attachment system that won't scratch your bike frame and allows for quick and easy access to energy bars, gels, or other items you need. This bag has a capacity of 0.4 liters and features one main compartment. It is made of PU leather material and attaches to your bike with durable nylon straps. The Fastfuel Bag Essential is designed to fit top tubes with diameters ranging from ø35 to ø73 mm and head tubes with diameters ranging from ø30 to ø50 mm. It measures 24 x 6 x 4 cm (9.4" x 2.4" x 1.6") and weighs 74 g (2.61 oz). Please note that sand, dirt, mud, and improperly packed bags can cause the bike frame paint in contact areas to become dull or scratched over time. To prevent any potential damage, it is recommended to protect the frame or rack with foam covering or protective film before attaching bags or panniers.