I bought the 2+ liters one which is in fact 2.4 liters, and I love it!

I stopped carrying Nalgene bottles, and scratching my head trying to find a way to fit a water carrier in a PSK. Nalgenes are heavy, bulky and still heavy and bulky when empty. My needs don't warrant this undestructible bottle. Just my opinion.

These Platypus bottles are amazing and deserve a place in your backpack/gear bag, but they won't fit in smaller PSKs.

Platypus collapsible bottles