The Increasing register plate adaptor comes with a plate size of 300mm x 300mm. This is used to connect one size of flexible flue liner to a different size of vitreous enamel stove pipe or stainless steel single skin at the bottom of the chimney stack. Made from stainless steel. Secure the bottom of the liner to the adaptor using self-tapping screws and seal with either fire cement/silicone sealant. Use the same procedure to connect adaptor to either your appliance or vitreous/single wall flue pipe. Colt Cowls Register Plate Increasing Adapter Specifications Plate Size: 300mm x 300mmInternal Flue Size: 125mmMaterial: Stainless Steel