ThermaFlue is a high quality insulating sleeve for flexible flue liners. Each sleeve is hand manufactured and inspected to exacting standards. The sleeve is stitched with stainless steel sewing thread braided with Kevlar, ideal for high stress applications requiring extreme strength and heat protection. Each length has an overlap collar with a D-G link system that ensures consistent thermal insulation. Adjustable Velcro fastenings facilitate a tight fit around the flexible flue liner.