This breather valve has been fitted to a Norton Commando motorcycle as part of an engine breather modification and the valve prevents air being drawn back into the motor via the breather pipe turning the engine into an air pump. The valve unit is small and ideal for the use I put it to.
I brought this valve to replace a broken valve on a 2013 renault clio 0.9. to buy the valve from renault would mean i had to buy the whole associated pipework to go with it at a cost of over £40. using this valve i just cut out the broken valve leaving the stubs in place and fitted the new valve using a few inches of petrol pipe. JOB DONE and i saved over £35