On my normal touring/city bike I use a regular middle priced bolt on collar(?). Works really well, does have some slippage (a few mm) over the course of a few weeks. On my MTB I use a Salsa QR seat clamp (no theft worries..the bike is under me or inside). Even though it is pricey it works brilliantly. Tightened correctly I usually have 0 slippage, and I use it at least twice during my normal route. I noticed for it to work right it has to be cleaned and re-greased about once a month.