Review (3/5): It's a good battery, but this is JUST for the battery
As previous reviewers have noted, this is a placement for a BATTERY and ONLY a battery. Don't be fooled into thinking you've found a $4,000 portable oxygen concentrator for a fraction of the price.
Regarding the battery though, what can you say? It's a good battery. A single battery for an EverGo can you give up to 4 hours of use, but more than likely will give you closer to 2.5 or 3. It all depends on your LPM setting. Odds are you will want to. The battery itself should keep its full charge for over a year and then slightly decline it's max charge hold. Also, realistically you'll probably want at 2 for your unit to get that maximum time before you recharge.
The price is okay for the battery. That's pretty much what everyone is charging. If however you're looking to buy 2 of them shop around elsewhere. Most companies selling the EverGo or EverGo batteries will offer a deal if you buy 2 and bring the cost per battery down closer to $225 or even lower.
If you are looking for the full EverGo equipment however, be sure to speak your doctor first. Portable concentrators are not for everyone, so you should speak to a professional about it. Also, if you may want to look around for a company like [...] or others who will do Medicare or insurance reimbursement for the equipment. At $4,000 it's tough to come out of pocket for that kind of money, and if you can find a company that will bill your insurance it makes it a lot easier.