Have now tried the 12 oz Camelback and the 12 oz MiiR. Camelback doesn't fit in the openings at all, I'm sending it back. The MiiR goes in, but won't go all the way down, so it sits high. I used it so I bought it. But it looks like the 10oz Rambler may be the way to go. One slight annoyance though, when the cup is in the holder, it's nearly impossible to get to the latch to open the armrest compartment.