Whats the plastic valve which comes out of the filter housing when i removed the oil filter in a mini cooper s?

i have just changed the oil and oil filter in my mini cooper s 2002 model and have found a plastic valve in the oil filter housing where does it go?Whats the plastic valve which comes out of the filter housing when i removed the oil filter in a mini cooper s?
Car accessories is our specialty. Upgrade your performance with our selection of air suspension, performance parts, performance chips .We provides all car accessories at very low cost.Whats the plastic valve which comes out of the filter housing when i removed the oil filter in a mini cooper s?
It usually comes with the new filter. It is to stop the oil from draining from the filter when the engine is not running. This keeps the filter full so that when you start up it doen't take any time to fill the filter before you get oil pressure.