Forget toy shop bubble fluid. This is the real deal professional fluid used to make giant bubbles with wands, and also for use in bubble machines.
500ml and 1 lt have the concentrate in the bottle, which you top up with TAP water. This assists in shipping weight and also lessens the possibility of leakage.
For the 4 lt pack you will need a 4lt plastic bottle to make up the full quantity.
For use in bubble machines you can dilute with up to twice the amount of water.