H Cowls are manufactured from stainless steel and are designed as anti-down draught devices. In normal or still air conditions, the hot gases and smoke pass up the chimney and exit out of the top of both of the vertical tubes. If wind drives downwards in turbulent conditions, the air moving down the tubes induces suction as it passes the horizontal tube and the hot gases and smoke exit out of the bottom of the vertical tubes. They are available in the size range from 4” – 12” with a stainless steel or sprayed matt black finish for use with stainless steel flue systems. There is also an 8” version available in a terracotta powder coated finish with toggle attachment clamps for use with clay chimney pots.