The Speedline Cavity Closer , Single Extrusion , with check reveal, is designed to provide a simple and efficient way of closing cavities inside masonry wall openings for windows and doors. This Closer is available in the following thicknesses: 50mm 75mm 100mm 125mm The insulated XPS core prevents thermal bridging by acting as a damp proof barrier and a substrate for plastering. Contact us today to find out more.