This is an oxygen concentrator. It was used for a Chihuahua weighing 2 kg. Usage time is 950 hours. When new, it was 90% at 1 liter, but it has decreased to 79%. However, it hasn't decreased much after 800 hours. As actual values, it's 50% at 2 liters and 40% at 3 liters. By the way, it was used at a little less than 2 liters. It was able to raise the oxygen level to 30% in a tent-type oxygen house. The manufacturer's guideline is 1000 hours, but the maintenance company recommends replacement at 3000 hours. Based on this information, I estimate it can still be used. The pump life is 5000 hours, and currently, there are no strange vibrations or noises, and there is no particular change from when it was new. The accessories include the main unit, silicone hose, remote control, filter, instruction manual, and everything that originally came with it. How about it as a sub-unit? If you purchase it by 3 PM, I will ship it the same day.