*Prevent the retraction of the exhaust gas, facilitate the suction, improve the combustion and protect the Chimney from external influences such as rain or snow. It can prevent strong wind from penetrating in pipes, chimneys, stoves, etc., thereby avoiding the adverse effects of houses. 304 Thick Stainless Steel Rotating Chimney Cowl Cap: Spinner Anti-Downdraught Fits Most Standard Chimney Pots Very effective in preventing wind and increasing ventilation. *Accessories send clamp,that never cause noises during rotation. The hat is constructed so that it turns under the action of the wind. The more the wind blowing, the more often the leaves turn and the stronger the air inlet from the inside to the outside. *Base diameter fits most standard Chimney with base diameter respectively of 100mm,110mm,150mm,160mm,200mm,300mm,350mm,400mm,450mm,500mm will fit standard Chimney pots, robust stainless steel construction .Can be installed directly without complicated assembly.