These are originally a medical eye wash bottle, but we use them for filling coolant into modern Trials bike radiators.

As the filler hose goes right to the bottom of the bottle you just squeeze the sides of the bottle to transfer the fluid.

And as many modern trials bikes dont actually require a completely full header tank, it is easy to fill and then release your pressure to "suck" a little fluid out leaving that prescribed gap at the top of the header tank.

As modern trials bikes don't have an overflow tank it's best to leave an approx 8mm gap from the radiator being completely full to allow for expansion, these make doing that really easy.

They are quite small holding 500ml which makes it easy to get into to tight and hard to reach spots, but enough for a coolant top up or change.

A real tool kit essential for a modern trials rider / mechanic.