This kit contains a hose with a 4" diameter, it is highly flexible, expanding from 300mm to 900mm. It is most useful where conventional hose and dust fittings are awkward to use and setup, due to it being flexible yet rigid as well, allowing it to be set to a position without the need to fix it permanently. Using the drill press or lathe, or simply using the router in a location rarely used, bend the hose to suit the situation, connect the appropriate fittings and away you go.