The ortlieb seatpost bag small is a versatile and lightweight option for cyclists one simple tool free manoeuvre is all it takes to fix or remove the waterproof seatpost bag made of pu coated nylon and cordura the integrated mounting allows quick change from bike to bike the roll closure with elastics ensures safe closing of the bag and allows tight packing this version has 15 litre capacity and is suitable as additional bag for longer trips the seatpost bag will protect the rider from s