These bulkhead adapters are CNC machined from aluminium billet. They step the hose size up from 1/2" ID, which is used on my range of heaters, to a more common 5/8" ID which is also the size used on most water control valves. The laser cut aluminium front panel is used to stop the CNC fittings from rotating when being installed and also serves to space them apart at the same distance as the fittings on the radiator matrix. There is also a narrow spaced version available if the heater is not being installed on a bulkhead. The bulkhead fittings and spacer plate can be polished with very little effort.