The 900mm x 900mm VELUX ZCU 1015 150mm PVC Extension Kerb for Flat Roof Windows (without flange) has been designed to work with the VELUX C-U, the kerb has been designed for use with warm roofs and flat windows. This kerb will provide your roof with additional height. The new generation of VELUX glass rooflights features 52% more natural daylight, reduced height, a new state of the art design that makes this range sit flush with your roof, discreet black corner keys for a smoother finish and new installation screws and prepared for craning. VELUX provide a 10-year guarantee on roof windows and a 5-year guarantee on electrics. Features & Benefits Comes without flange Designed to work with VELUX C-U Provides your roof with additional height Part of the new generation of rooflights