The Anthracite Grey Inaba Denko Slimduct Flexible Joint is part of the Anthracite Grey Slimduct Trunking System; its easy to install and adds the finishing touches to an air conditioning, refrigeration, or heating installation by covering up unsightly pipework. This quality duct is fire proof and UV resistant meaning it can be used internally or externally. This 100mm Duct range is for pipe sizes up to 3/4" and 7/8" with 13mm insulation.