Difficult to use and naturally expensive. They wear out very quickly and the cost of replacement is almost with every haircut (1 hour). Bad purchase

Excellent!
Very easy replacement of the trimmer line, just needs to be inserted correctly: It should be inserted in a way that it just comes out from the other side, without protruding.
It is very easy to install on the lawnmower.

I used it with the Husqvarna 553RS (50.6cc, 3.1Hp). At first, the machine kept shutting off...(even though it was warm). Maybe it's too heavy for this specific model or maybe I didn't find the right RPMs... As soon as I gave it a little gas to start, it would shut off... At some point, it worked at low RPMs and the head performed well with 2 pieces of 3.3mm trimmer line (Stihl CF3 Pro). However, I found a concrete block and the trimmer line got stuck in the head, making it impossible to remove the remaining line by hand. You need pliers to remove it or an Allen wrench to open the head. Since I didn't have either of those nearby, I gave up and switched to the classic semi-automatic head to finish my work. It's convenient that you don't have to unscrew anything to put the trimmer line pieces in, but I did encounter a small difficulty in pushing them in to fit in the head. I suppose with thicker trimmer line, it would perform much better. I will try it again and if there's anything new, I will mention it.

Unbelievable head. Goes in and out fearlessly. I had an aluminum one and it broke when I took it out. This one is wonderful.
Also, the ease of putting on new fishing line is unmatched! Unbelievable!!!!!

It is similar to the Oregon Jet-fit.
Only that logically it is a different construction... It worked fine