The collar is hinged so it can be fitted to existing pipes and is locked with a steel clamp. It contains several layers of high pressure intumescent compound which are flexible – allowing a comfortable fit over nominal pipe sizes: 55mm, 82mm, 110mm, 125mm and 160mm. During a fire, the pipe softens and the intumescent material expands to completely fill the gap left by the pipe. FireClose can be cast-in or surface-mounted (brackets are included) in either vertical or horizontal planes. It is slim enough to fit into narrow corners which would be too tight for larger closers. It provides up to 4 hours protection, depending upon the substrate. Non-standard sizes are also available.