I was using this to investigate my wife's affair. I've used it for about two months. There is no box or instruction manual. Operation has been confirmed. The regular price is about 3000 yen per piece. The capacity is 16GB. You can connect it to a PC with the included cable and listen to the recorded content. To use it, simply turn the power ON to start recording. Here's the Amazon link for the product: https://www.amazon.co.jp/gp/aw/d/B08L3C8FY3?psc=1&ref=ppx_pop_mob_b_asin_title