A non-woven form of glass cloth used for reinforcing polyester resin. The strands of glassfibre are two or three inches long and they lie in random directions, held into a sheet by a small amount of resin. There is just enough resin to retain them in this form for convenient handling, and when laid in place the mat is thoroughly permeated by a far greater amount of polyester resin. Most ‘fibreglass’ boats are built principally of CSM, though woven rovings are also used.