This is a noise filter from IsoTek, a manufacturer of clean power supplies. It is a domestic genuine product, purchased new and used by a single owner. When I plugged the power plugs of my DAC into a power strip with this filter in between, I felt that the background noise was reduced and the sound became clearer. This is a personal opinion, but based on my experience, I recommend using two or more. I think it's also good to use it by plugging it in near switching power supplies and chargers that generate noise. It's easy to use because you just plug it into an outlet. Also, the ability to plug it in various places and check for changes and effects is appealing. There may be some signs of use, but it works without any problems. There is a shallow scratch on the upper side of one unit that doesn't catch a fingernail. *The unit on the left in photo 4 I don't remember dropping or bumping it, so I think it was made during manufacturing. Power-on confirmation has been done. I used it for noise reduction in a smoke-free and pet-free environment. It was used and stored in a room with humidity control. I am selling it to organize my audio equipment due to changes in my living environment. Depending on when you purchase it, I can ship it the same day. I will pack it carefully and ship it, so please rest assured. *Search keywords ISOTEK NOVA SIGMAS TITAN GENESIS AQUARIUS Nova Sigma Titan Genesis Aquarius Clean Power Supply