Sflue | 2141306 tee | 152mm 135° tee | twin wall flue | stainless steel chimney tee | HETAS approved flue fitting | solid fuel & gas/oil flue component | chimney inspection tee. TheSflue 2141306 Twin Wall 135° Tee – 152 mm Ø is a high-quality flue component designed for robust performance and safety.