The quality of construction is good. The key does not fit perfectly, I think it should have been a little longer

Very good. It facilitates incredibly.
The only thing I wonder is why they made it so small.
The part/container that fills with water could be three times bigger, lengthwise (because widthwise, I understand it would 'hit' the wall) and a little deeper. Why should I empty it 2-3 times for each radiator, when one time would be enough... if it was slightly bigger?
While it is very good, this little issue seems to reduce its usefulness.

I got it all excited. On the third use, the nozzle broke, something I have never experienced before. I don't know if it was defective, but I was completely disappointed because firstly it cost me money and secondly I didn't get to enjoy its practicality. I mention this fact so that it exists as information for any potential interested party because if someone had mentioned this, I definitely wouldn't have bought the product.