Hi all, I'm thinking about replacing my QR levers -- after some hunting, do you think any of these would be a good choice?

http://harriscyclery.net/product-lis...1-m25260-qc49/

I read (http://sheldonbrown.com/skewers.html) that "enclosed cam" QRs like these might be better than the "exposed cam" that came with the bike, because "enclosed cam" QRs don't get all gritty.

If these are a good choice, can somebody help me understand whether I need 6x50mm, 8x50mm, or 6x60mm?

Or is there some other good choice?

Thanks!