Composed of galvanised, perforated metal sheet with a thickness of 0.8 mm, with injected polypropylene wheels (polyethylene in the case of -30ºC) which are mounted on a polished steel axle of 3 mm diameter. Precisely cut to ± 1 mm, the material is always cut, mounted and delivered to the length indicated by the client. The distance between wheels is 33mm. With rimmed wheels, the required minimum distance is 49.5 mm. The 4 mm diameter hole used in the base eases the later fitting of rivets and screws.