Hat designed to rotate with the action of the wind, so that the more the wind blows, the more the blades rotate, and the more powerful the air intake is from the inside out. Rotating hood for ventilation pipes, smoke chimneys, and air extraction.The gairing provides maximum protection without hindering the performance of the chimney. Thick Stainless Steel Rotating Chimney Cowl Cap: Spinner Anti-Downdraught Fits Most Standard Chimney Pots Very effective in preventing wind and increasing ventilation. Base diameter fits most standard chimney with base diameter will fit standard chimney pots, robust stainless steel construction