The Spark Arrestor (by Colt Cowls) is designed to help reduce the risk of sparks leaving chimney flues. Spark Arrestors have two mesh inserts, the inner mesh catches debris and the outer mesh slows any escaping gasses. Construction - Aluminium and steel. This cowl is coloured terracotta.
This items is used to prevent sparks from leaving the chimney which may cause a fire, normally used for easily ignited roofs such as thatched or shingles or  if your chimney is close to a thatch or shingle roof.
Spark Arrestor Chimney Cowl fit Chimney Pots from 125mm - 250mm

Spark Arrestor Chimney Cowl