I'm assuming you're reffering to the "o" rings...

When you take the cover off the oil filter housing you noticed the long shaft attached to the cap? The bottom of the shaft is where the small one goes.

The larger ring goes on the underside of the lid to the filter housing.

Don't know what it will do if you don't install them. I would think the cap would leak without the larger ring installed but the smaller one???

I'm sure some of the more senior members will know...

Cheers,

Bill