Seatbag with two-piece, removable bag. The harness can be fit to the saddle tube with a velcro fastener, and the side straps can be threaded under the saddle sticks to attach to the side buckles. The lower and saddle-side sections are thick tarpaulin, the rest are woven PTP. The harness is two-layered everywhere due to the heavy strain. The bag material is also impregnated with PTP, which is a single layer. After folding, the ends can be tied with a rope to the saddle and tied on the saddle tube. This gives much more stability than similar bags, even on very poor terrain.