The principle is simple: by the water pressure in the hose is a constant amount of fertilizer brought in and thrown out with the spray gun.
But the device shines with thoughtful details: the pick-up tube for the fertilizer is loaded with a weight so that it always depends on the lowest point of the container. So you can also work well side and semi-erect.
By 1.25 the container is also suitable for larger gardens (with more to fertilize plants) not too heavy, you can easily and effortlessly carry around with him - and he still has a sufficient range that I do not have to refill every few minutes fertilizer.
In my eyes, a class part!