These consist of two die-cast elbows one of 60mm diameter and one of 100 mm diameter. The 60mm elbow is mounted in the 100 mm elbow and secured together by means of two screws through the sides of the elbows. The fundamental characteristics of these elbows are there robustness, perfect air tightness and reduced flow resistance. Available in different versions, for example female with 100mm diameter ‘O’ ring seal and flue gas analysis test points.