I had high hopes for this adapter, but I think it's really unfortunate execution of a promising concept. I travel a lot and have fully transitioned to wireless earbuds, so I always carry a simple Bluetooth adapter with me. I also need to carry an audio cable for that one, though, so I was hoping this would help reduce the bulk in my bag.The first thing I noticed when unboxing the 1Mii adapter is that the charging case for it is enormous. It's larger than any of my sets of portable earbuds by a significant margin - it's approaching the size of a full Altoids tin, but thicker. I have an onboard kit I keep all my travel accessories in, and the case is too big to fit in it.The design of the adapter is one of those things that looks great until you think about it a little more closely. There are two flippable blades, but despite the prongs slightly protruding from the adapter when closed, you have to flip the blades out the back of the device to use them. You can flip one or both, depending on whether you need a single or double-jack connector.The double-jack connector is a nice feature, but almost all US domestic airplanes only need a single connector; the double is mostly used on international planes in business/first class where they don't want you taking the headphones with you after your flight. And even then, on recent international planes, one of the prongs of the double jack can be used by normal headphones, so it's actually likely you won't need the adapter at all, even if the plane looks like it requires one - just try the other pin if you only get mono sound.I tried this adapter out on a Delta A321neo aircraft in first class. On that aircraft, a single prong socket was provided on the in-flight entertainment screen. I tried plugging this module in, but it wobbled around and I wasn't sure it had connected - it seemed like the pin didn't go quite deeply enough into the socket. It did make a connection, but a tenuous one.The bigger problem I had was with connectivity to my earbuds. I tried with a couple different brands of wireless earbuds, and I had a nightmare of a time pairing them. The module has only a single button and single blinking color LED, so you don't get a lot of feedback while you're troubleshooting; a chart of light blinks is included with the device, but unless you bring it along you won't know what a cyan vs green light means. I did get connected, but I experienced periodic dropouts while trying to listen to content.Another issue I encountered was that the volume level coming out of the airplane was too low, even at maximum volume. There's no volume adjustment on this device, and my earbuds couldn't crank up high enough with their own volume settings (which are themselves cryptic to operate). So if you face a similarly limited source device, you might be out of luck and unable to hear the content from the airplane.A set of various adapters and cables is included to work around the inflexible design of the module itself, but they just serve to highlight the design quirkiness. If you use the extension cable, which makes the form factor more traditional, it has to attach to the blades after they're flipped out on the back - it can't slot into the blades while closed, so the whole thing looks kludgey and is hugely bulky. I think you probably need to pack these cables to be assured of being able to use all airplanes - the adapter is too inflexible to ensure it fits in all possible socket configurations, which defeats the purpose of having the connector integrated in the first place.I definitely recommend picking up a Bluetooth adapter so you can enjoy in-flight entertainment on the go. I just don't recommend this specific product.