I have an FSA orbit MX headset, but I lost the little rubber seal at the bottom of it and I'm not using one. I was wondering if I need it or whether it makes no difference. The set-up goes fork, crown race, a seal, bearings, cup, then the top cup, bearings and another seal and my compression ring. also If i have no top cap will that make a difference. To avoid confusion the headset came with a rubber circle like one that comes with a threaded headset then another smaller seal that sits on the bearings.