The suit consists of a synthetic material and in order to limit its influence on the performance there are strict regulations which are checked randomly at the competitions. It is only allowed to be 5 mm thick and the air permeability is limited to 40 l per m² and second. It is measured at various points (e.g. upper arm, chest, waist, thigh) and the size of the suit must not be more than 6 cm bigger than the girth.