I put a set of these on last year and they work very well. I use the hand pump with the squeeze ball. You can't overfill them. Very easy. I put some pictures in my library. http://www.flow-rite.com/battery-watering/qwik-fill
I've used them for many years and they are well worth the money. I'd recommend them, especially for those with hard to reach batteries. Makes topping them off very easy.