So, here's the deal. Below, a user who opened the device to fix it because it had some issue, in his detailed description, writes that the device has a gas discharge tube, which is indeed true. He also mentions that it has 3 MOVs with 2 thermal fuses, which is also true. He further states that it has an anti-interference capacitor for noise filtering, which turns out not to be true.

Obviously, the product description was made based on what he read either from the manufacturer's page or from the packaging or from the component he saw when he opened the device and thought it was a noise filter, while in reality, it's just a fuse. Besides, as I mentioned above, the manufacturer's website states that there is EMI/RFI protection filter up to 70 dB, and the same is stated on the box.

However, out of curiosity, I unscrewed the device to see if everything mentioned by both the manufacturer and the user below is actually true, and also to see if its construction is comparable to that of APC, since APC no longer manufactures surge protectors.

I will also attach two photos and circle the component shown in the photo, which ultimately is not a noise filter, but simply a 6.3A / 250V fuse – type T, where T means it is slow-blow (delayed response).

As for build quality, both inside and out, the device is just fine. But the question is: why so much misinformation in the specifications?

Why do you tell me it has a noise filter when it actually doesn't? You "stick" in the specs that you have a filter, but in reality, you don't.

And I said: 1300 Joules, more than those of APC — great! I also saw a mention of a noise filter and said "perfect, I found the replacement."

But... nope.

So, the reason I remove 3 stars is this. And I continue the search for a single-outlet surge protector that matches what the APC one offered

As far as the plastic construction quality is concerned, it is mediocre. Additionally, the internal plastic protection broke easily when the device was not plugged in. If there are children in the house, it is better to go for something else. Some other power strips from Apc, Eaton, Brennenstuhl are of better quality and more durable in their construction. As a surge protection, during the 3 years that I had it plugged in for the exclusive protection of my hifi system, I did not have any issues. This specific one from Crystal Audio, along with a good simple multi-plug without a switch, is suitable. This particular product is primarily intended for hifi systems, and then for other devices such as refrigerators, TVs, air conditioners, etc. It also has an EMI/RFI filter. If it is used for a medium to good sound system, it is better than the Apc power strip, but worse than the other two. In my personal opinion, after many tests, for those interested in surge protection for a medium to good sound system without wanting to exceed the budget, it is preferable to choose Eaton or Brennenstuhl without an EMI/RFI filter, as they will have the best sound performance and better construction quality, provided they live in an urban area without many power issues.

Equivalent to the basic APC (without USB) single socket. It has 3 MOVs that bridge phase with neutral in case of overvoltage and 2 thermal fuses connected to the MOVs that burn when the MOVs get too hot and the LED light goes off (then the socket needs to be replaced as it no longer provides protection). It also has a gas discharge tube that bridges with grounding in very high overvoltages. And an anti-interference capacitor for noise filtering.

Like the APC (and all surge protectors for home use), there is no way to know when the gas discharge tube stops providing protection. One solution is to have two or three always connected in the house and replace them when the LED goes off (they not only protect the connected device, but also nearby devices - possibly even the neighbor's :P).

I deducted one star because out of the three sockets I ordered, one had a problem on the circuit board (broken trace), which took me a minute to fix with a soldering iron, but it shows a lack of quality control. If someone had simply plugged it into the socket, they would have seen that the LED did not light up. I also bought a power strip from the same company and I am generally satisfied.

Disclaimer: I am a simple DIYer, so there may be inaccuracies in what I write.