There are lots of ways to transfer files between your PC and an Android device, but the simplest method has been to tether one to your PC using a cable. SanDisk has a better idea: Its Ultra Dual USB Drive can be used with Android smartphones and tablets and with PCs.
The thumb drive has a standard Type A USB 2.0 plug on one side, and a Micro-B USB 2.0 plug on the other. I tested the 32GB model with an HTC One smartphone. Both of the drive's connectors are protected by a sliding plastic shell that automatically retracts when you push the plug into a USB port (you'll need to pull the covers back out when you unplug it). Due to the thickness of the thumb drive's shroud, I had to pop the bottom of my phone out of its Speck case. But I've encountered the same issue with right-angled headphone plugs, so this isn't a showstopper by any means.
Having both connectors makes it extremely easy to transfer files between your Android smartphone or tablet and your PC. Move or copy files from your phone to the storage device, unplug it, plug it into your PC, and move or copy those files to that device (and vice versa). If you use a cloud-storage service, you can copy files there as well. The storage device measures just 1.5 inches long and 0.75 inches wide. It has a lanyard ring so you can add a tether, but the hole is extremely small.
The HTC One doesn't have its own file-manager software, although there are a number of free Android apps available in the Google Play store. I've been using ES File Manager for a while, but I've since switched to SanDisk's free Memory Zone, which has a much more polished user interface. Rather than having to drill down into the phone's directory structure, Memory Zone indexes and sorts all the files it finds on the phone and on any storage device that's plugged into it. You can add any cloud-storage services you use--such as Dropbox--and the app will index all the files stored there as well.
Once the files have been indexed, you can press the music icon to see a list of all the music files in storage. Press the landscape icon and you get a list of all the photos. There are also icons for movies, documents, and apps. Tap the file, and a Complete Action Using pop-up menu appears. If it's a music or video file, you can play it with whatever media player apps are installed on the device. If it's a photo, you can view it using your favorite photo editor, and so on.
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