"220V AC Cooling Fan" keep me warm winter power tool, mainly with a ceramic lamp, prompting the inside air convection, and thus achieve a faster heat up, the purpose of the thermostat, and more efficient use of heat. Assembly needs a little bit of ability, easy to install, simple to use, plug and play! If you are not sure it can be installed and used correctly, please do not shoot, not as a reason for the difference in assessment. Family "220V AC Cooling Fan" in-line products in the open, because the fan rotation, there will be a little sound, basic sound like the same size USB fan, will not be completely silent, if not mind, please do not shoot, not to this is the reason for the difference in assessment! The muted effect 12V USB paragraph better, but relatively wind than "220V AC Cooling Fan" of smaller, there is no so-called best of both worlds, but also to do the best it! Haha!