Unique inert polypropylene tubes offering storage of maps, plans and materials housed in roll form. Independent tests have established that the Chartpak system has a neutral range pH and does not contain any additives that might migrate at any point in the future. The static free polypropylene units are, with end pieces in place, dust and waterproof. Chartpak's unique design prevents discolouration or fade damage from UV radiation. Diameter 95mm.