Purchased for Car Audio with USB MP3.

For this job, it is PERFECT as it is small, does not protrude, and therefore does not bother (no risk of breaking or damaging the stereo connector due to careless movement).

Additionally, it does NOT heat up when used in the stereo (the fact that it is USB 2 and not 3 helps).

If you want to buy it for a flash drive on keys, there are "better" (and faster) solutions made of metal without a cap (which will be lost if it bothers someone). This one here requires a string to be attached to the keys (which can be cut), while other small (maybe not as much) metal ones can be directly attached. So for a flash drive on keys, look for other metal options that are structurally better.

Note that it is not very fast, not even for USB 2 (we said it is not USB 3). I haven't measured it yet, but the manufacturer provides 16.5 MB/s reading and 6.5 MB/s writing, which is probably slightly worse in practice. But when you want it for car audio/mp3, speed is not a major concern (how often do you write songs and how many are they). It is more important that it does not heat up, and this satisfies that criterion.