O2COOL 10-Inch Portable Smart Power Fan

I decided to buy this to take on future trips to Europe. It is extremely hot in Europe regardless of the season. The trains are very hot winter and summer. The hotels are hot and many don't have air conditioning, or they refuse to turn it on even when it is really hot. I've found that even when it is 60 degrees outside at night, opening a window offers little relief, because the cool air doesn't come into the room. So I wanted a fan that was small enough to use on a train, or perhaps even an airplane, but large enough to assist in bringing some cool outside air into a hotel room. I haven't taken it to Europe yet, but I've experimented with it at home and this fan looks like it will be perfect for my intended use. It is dual voltage, which means I can just use a plug adapter and use it in Europe. It provides a reasonable amount of wind force; certainly all I could expect from a 10" fan. I've charged it and then let it run until the batteries discharged, and it ran for quite a long time, although I didn't measure it. I doubt I will use the backup D-battery capacity often, but that is nice to have. The legs are easily removable, and this fan fits easily in my eBags TLS Mother Lode Weekender Convertible (Solid Black), which I take onto planes to hold my computer and electronics plus a change of clothes. For what it's worth, the fan will stand up without the legs, and that might be how you would want to use it on a plane or a train. I think this is the most expensive O2 fan because of its use of three power sources; the fan will automatically use the "cheapest" option, first plug power, second the internal battery, and third the D batteries to run the fan. This can be a pretty good thing. The USB port is only for charging things like a phone; you cannot charge the fan through the USB port. The inner fan unit has almost unlimited vertical tilt ability to allow one to adjust the direction of the air flow. I checked the weight using my bathroom scale, and the listed weight of 3.4 pounds looks about right; without the power adapter the weight is about 2.5 pounds. A couple of reviewers have complained of a lack of quality; I did not find this to be a problem, although this is a plastic fan and I can see how there might be some quality control issues; it seems quite sturdy to me. I have seen complains about other O2 fans that the battery will not charge, and it certainly will not charge when the fan is in the "OFF" position, only in the "STOP" position. I think this fan has an automatic shutoff, but with battery operated devices, once the battery is charged you should unplug it as overcharging the battery for an extended time will ruin it. Also, when buying this for occasional use as I did, you should take it out every couple of months and run it until the battery discharges completely and then charge it up again, as this will maintain the battery; don't just "top it up." Having left my glowing review of this fan, I should note that the current price is substantially more than I paid. What seems to be an identical fan, O2COOL 10-Inch Portable Smart Power Fan with AC Adapter & USB Charging Port, is being offered with Amazon Prime shipping. Since I believe these fans to be absolutely identical, everything I said about this fan applies to that fan. Just choose the fan with the lower price.