I'm not a fan of the umbrella seals. These used to be really good, but the ones out there today last about a year or two at best. Once they crack and split, you're left with no seals. And Jerry's comment about not using both is spot-on. You don't want to starve the valve stems of lubrication. Personally I use the o-ring type and leave it at that. I think I paid $1.80 for a set of 12 from Rock Auto and if you catch them on a mfg closeout offer, they're about 8 cents each.
