The RAINPROOF SEAT 5.0 saddle bag for mounting on the seat post is made of waterproof 800D nylon. The bag has one main opening at the back which gives access to one large pocket for storing spare clothes or other bulky loads. The bag adapts to your load thanks to the rolling system. It can be increased or decreased according to what's inside. It is attached to the seat post and saddle rails using three straps. In addition, it is equipped with two types of spacers between the bag and the seat post (depending on the type of seat post - round, oval, smaller or larger diameter). The bag will stay in place even during shocks. Like other bags from the RAINPROOF series, it is made of waterproof 800D nylon with seamless bonding and an additional TPU coating.