Blue Koolance high performance liquid coolant. The bottle includes a flexible rubber funnel and small segment of 1/8" ID tubing to make reservoir filling easier. Pre-mixed with corrosion and biological inhibitors. Non-toxic.
The total amount is 700cc (23.67 fl oz), which should be a little more than you'll need to fill a typical Koolance system.
WARNING: Not for internal use...you sicko...