I recently tried these with the 8oz Playtex bottles. They seem to work well. So far, I have had no leaks with any of the generic liners. The only problem I have is that the measurements on the bottle holder do not match the actual number of ounces of liquid in the liner. For example, I put 6oz of liquid into the liner and it comes up to the 7oz line on the Playtex bottle holder.
I don't know why the measurements on the bottles and the liners don't match up, but it's really difficult to tell how much baby actually ate. I'm not sure if the bottle liners have the measurements marked on it. If it does, they are very faint because I have never noticed them.
This issue with the measurements is the only thing I would change with the Parents Choice bottle liners. Otherwise, they work great - no leaks, no wasted milk.