Fuel filter kit

[Brady D]

I’m replacing the fuel filter on my tractor and I saw a kit with a new bowl, filter, o-ring for the bowl but then there is a very small o-ring and a spring what is the spring and small o-ring for

 

[K5lwq]

The o-ring goes on the tube inside the filter housing. The spring goes under the filter and pushes the filter up to seal it to the small o-ring.