material The tail box is constructed from 1.5 mm thick aluminum alloy, providing durability with strong compressive and loadbearing performance. Protection from the elements The box features a leather lining that is waterproof and moistureproof, helping protect contents from wind and rain and keeping items dry. Secure and convenient closure Doublelock antitheft design with a onebutton quick lock on the box for secure closure. Capacity by size 28 L: fits 1 half helmet 36 L: fits 1 small full helmet 45 L: fits 1 full helmet poncho 55 L: fits 1 full helmet 10 bottles of water 65 L: fits 2 small full helmets 80 L: fits 2 full helmets 10 bottles of water 100 L: fits 2 small full helmets 2 half helmets Use scenarios Daily commuting: choose 28 L or 36 L to carry a helmet and small essentials while staying compact and easy to handle. Weekend rides: 45 L or 55 L accommodates a full helmet plus rain poncho or water for short trips and unpredictable weather. Longer trips or shared gear: 65 L, 80 L, or 100 L provide space for two helmets plus water and additional gear, suitable for extended rides or family trips. Key benefits Durable aluminum construction supports reliable everyday use and long service life. Protected interior keeps helmets and gear dry in wet conditions. Easy and secure access with a reliable onebutton closure enhances security. Clear capacity options help you choose the right size for your helmet needs and accessories.