This is an oxygen analyzer for Nitrox (Enriched Air), the **NuVair O2 Quickstick (oxygen analyzer)**.  The main unit has been working normally until now, but it has stopped working due to the sensor reaching the end of its lifespan. Therefore, it is a **junk item (as is) that requires sensor replacement**. The sensor is a replaceable electrochemical sensor specifically for this model, and can be purchased at online shops (new sensors generally cost in the range of 18,000 to 20,000 yen).  I am not planning to use Enriched Air (Nitrox) in the future and do not intend to purchase a new sensor, so I am selling it. Everything in the photos is included. Please understand.