The VELUX Insulation Collar with Underfelt Collar 66 X 118cm is a high-quality product designed to enhance the installation of roof windows. This collar ensures optimum energy efficiency by eliminating thermal bridges between the window and the roof structure. The underfelt collar, made to fit perfectly with VELUX roof windows, provides a secure seal for weather protection. The product is easy to install and adds an extra layer of insulation, enhancing your homes overall energy efficiency.