28x15mm External/Internal Solder Reducing Coupler - M-SRRF-28-15 From copper and copper alloy. Designed for jointing copper tubes to BS EN 1057 in hot and cold water services, in small bore and mini bore central heating, low pressure steam heating, and in-vented/un-vented closed circuit heating systems. WRAS approved. Manufactured to BS EN 1254 Part 1