One-and-a-quarter inch BSP steel joining nipple (approx. 41mm outer diameter).
Used in conjunction with gaskets to join sectional cast iron radiators together. Right hand (normal) thread on one half and left hand (reverse) thread the other side. When the nipple is turned, the two radiator sections are brought together, compressing the gasket and forming a watertight seal. On this nipple the serrations denote the right-hand thread side.
1.25" BSP is the correct size for Castrads' Grace and King ranges. May also be used with many other brands including Roca and Idea Clima.