The little copper or aluminum washers that go on the drain plug that is. I changed the oil & filer on may XR284 and must have lost the washer at some point in the process. Not on the floor and not in the drain pan so I'm not sure where it wandered off to. Well everthing held tight while I warmed it up and went for a ride because the level was fine when I checked it post ride. I then put the bike back in the trailer, came back 2 days later to get the pop-up for a soccer tournament weekend and I find all that nice clean fresh synthetic oil on the rubber bed mat that is on the floor of the trailer. If you didn't know XR's hold a lot of oil, like more than a quart, more like 2 quarts. So I had a nice mess to deal with a a big concern that I punched a hold in the case or something until I investicated the path of the oil and found the litle washer MIA. You'd think I'd just replace them every oil change since I ordered 5 replacements from Service Honda a couple years ago and they ended up sending me a bag of 50. I guess that will be my new plan, too bad it took a mini Valdez spill to make it happen. DOH!