I'm guessing that 'collar' means non quick release. Anyhow, I'm using a black anodized Salsa collar on one bike. It does seem to have solved any problem with slippage, though I'm not sure why. Also, it not only looks good, but if someone wants to steal the seatpost and saddle, at least they will need an allen wrench.
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Some people are like a Slinky ... not really good for anything, but you still can't help but smile when you shove them down the stairs.