The VELUX Insulation Collar with Underfelt Collar 55 X 78cm is a top-tier, energy-efficient solution designed to enhance the performance of your VELUX roof windows. This product ensures a secure and tight seal between your window and the roof structure, thereby reducing heat loss and improving energy efficiency. It also includes an underfelt collar to create a weather-tight seal and protect against rain. Easy to install, this insulation collar is compatible with all standard VELUX roof windows of corresponding size.