The EF (Easy Fit) is a worm gear clamp for fixing round ducts such as the ducts used in ventilation systems. This type of worm gear clamp is known as a duct clamp and works similarly to how a cable tie does. The duct clamp has a minimum clamping diameter of 25mm and is available all the way up to 750mm. It has a band width of 9mm. The band is pressed, folded up at the edges and has a smooth inner surface.