Bestem liners are constructed from high quality weather-resistant heavy duty 1680D nylon. The bag will never sag and will stay in shape even empty as all edges are enforced with plastic pipes. With so many features such as easy carrying shoulder straps, heavy duty carrying handles, heavy duty water-proof zippers, and reflective 3M Scotchlite stripes etc., these liners are custom made to fit each bike's pannier system like a glove.