Calor Essentials Propane 37mbar 2-Cylinder Auto Changeover Valve with OPSO The Calor Essentials 2-Cylinder Auto Changeover Valve with OPSO is a top of the range automatic changeover system that gives you continuous, safe propane gas supply for your appliances. It automatically switches from an empty cylinder to a full one, eliminating downtime and with advanced safety features to protect your installation. With OPSO (Over-Pressure Shut-Off), Consumer Safety Reset (CSR) and non-return valves, this changeover kit prioritises user safety and reliability. The Le Clic changeover head with reserve indicator shows you which cylinder is active and the weatherproof ABS casing will last for years in harsh outd