Great system, ornce the ice cube is properly Formed inside the bladder the cooling effect is great with both 5l bladder and dual 4l one.However,I noticed that the 4l dual bladder is leaking through the cap opening due to a lack of proper seal. Also the use of the central pocket is working untill the connector on the central lower side of the bladder is pushed against the ice. Then it gets stuck due to the pump suckcion. It would be great to upgrade the connector or the system in order to prevent that. Once stuck the pump can't properly pump the water through the pipe. Once in the backpack, the backpack pushes the connector against the ice and it gets stuck really quick.It makes it unusable for this usage once inside the backpack.