three stars because the Allen key doesn't fit to tighten the screw... and so we weren't able to install it to use it...

I replaced the automatic plastic head (~300gr) that came with the 40V battery in the package and which was, to put it politely, cumbersome.
The Nakayama weighs ~200gr and I put two opposite pieces of 2mm line that I cut from the plastic head... okay, it cut more grass than expected before they broke apart.
Then I tried with one ~3mm piece that comes with the Nakayama and it cut thick stalks and dry grass easily.
The PB300 is tremendously more user-friendly than the original head.
The Total TSTLI20018 at 37 Celsius, after the 15 minutes I ran it to check the PB300, got a little warm at the angular head and I think that for such a machine we want no more than 2.4mm and probably only one piece of line, i.e. with 2 ends coming out of the head, gives us the best result.

You throw away the trimmer lines it comes with and put in a 4 mm line, and the head cuts everything from weeds to even breaking canes. An incredible head, and it is also universal for all brush cutters

The product that was delivered to me is not the one shown in the photos. The Allen screw is on the side instead of on the top, which causes a problem in securing the trimmer line.

It fits easily and you can easily change the line. The screw got lost immediately, it needs to be tightened a lot. I put another one. However, the biggest problem is that when I wanted to remove it to change the head, it was extremely difficult. I took it to a shop and it took them over fifteen minutes to remove it. That alone is enough for 1 star. You get what you pay for.

Very convenient, it fit easily, the lines also go in easily, the screw needs tightening at regular intervals because it loosens, once it came off but luckily I found it and continued.

Top-notch, it cuts very low, boots are now essential as it throws everything it finds, I leave it on the ground and it reads the terrain, with 3.5 line everything is even

The best head of all the ones I’ve tried! For electric, I use 3.5mm square twisted trimmer line, and for gas-powered, over 4mm. The only negative was that it came with the wrong Allen key size in the package.

I also got a second one (I uploaded a photo of the second one); it comes in NAKAYAMA packaging, has the correct Allen key, and looks good!

I had a bit of trouble fitting it on a Stihl because it actually needed a larger spacer. But it does its job just fine.

Perfect - just indeed the Allen screw needs to be tightened very well. Well-balanced and very easy to fill. At this price, I can't find anything better.

It doesn't fit thick fishing line over 4.0mm. Useless for me. It doesn't say that in the description. And it's lucky to get 1 star.

No relation what I saw and ordered with what they sent. Simple Chinese that I find for 4 euros, I would have bought 2 and I would have change

Very powerful. Few vibrations at the beginning disappeared after a few minutes of use. I have only used it twice for 2 hours. For now, it seems perfect

Good quality. Easy trimmer line replacement. I use the 3mm size.
The store advised me that due to its larger weight, it is not recommended for use in an electric grass trimmer as it may cause the motor to burn out.
Nevertheless, I decided to take the risk. Money is not an issue :P

Looks good. I had fewer vibrations on my grass trimmer (plus kw-520 M) compared to the plastic one. You can also use a thin nylon string if you use 4 pieces instead of 2. What I didn't like is that it doesn't come with any installation instructions, nor screws/bolts to attach it to the grass trimmer. I used the screw from the disc.

It does its job just fine. The downside is that the opening screw is at the bottom, so you have to almost fully lift the entire machine upright. Other than that, changing the fishing line is fairly easy.

I have used it 3-4 times and so far I am satisfied. Properly balanced, easy to change the trimmer line.
The only drawback is the trimmer line it came with. The two pieces were rather small and broke quickly, but this is of little importance. I use a 4 mm trimmer line and everything is fine

Very durable head for thick monofilament lines. In combination with a high-quality monofilament line, it will definitely serve you well.

Very good and user-friendly. Works without any problem. By placing a slightly longer screw, it also takes thinner fishing lines

Excellent product, very well balanced and easy to change the fishing line. What you should keep in mind is that if you use a fishing line with a thickness below 4 mm, the Allen screw that secures the fishing line does not have sufficient length to immobilize it completely.
With a 4mm fishing line placed in two pieces diagonally (i.e. 8 mm), you are absolutely guaranteed.
For the price it is offered, it is worth 1000% of the money you give, do not waste money on more expensive ones, better to buy a good quality fishing line.