Those two o-rings and the large o-ring for the filter cap seal should have come with the filter. You can remove the filter and install the o-rings when you get them, and just reinstall the filter. The larger of the two o-rings on the filter stem will also fit the dip stick, so you might want to buy two. When you change oil, loosen the cap on the filter enough to let air in so the oil will drop into the pan and can be drained off. I love this oil filter arrangement. No more laying under the car with oil running down your arm trying to remove a hot filter screwed sideways into the block.

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'97 E 300 D