Rover 75 / MG ZT CDT/CDTi Thermostat O Ring - STC4540 (Thermostat to Heater Rail)
This item is kept in stock for same-day dispatch.
This is the much-fabled blue Viton O Ring, fitted to seal the metal heater rail to the thermostat housing.
When you change the thermostat, you'll normally need to change this too - and most thermostats don't come with this seal included. There is an option to add this to the thermostat kit from ourselves - go to the page for the thermostat, and use the drop-down menu to add the O Ring.