Let me start by saying these earbuds are exactly what you'd expect for under $20 - they're not going to blow your mind, but they get the job done... mostly.
The magnetic design is actually pretty cool - they snap together like a necklace when not in use. No more tangled wires! I've used them for walks and light workouts, and they stay put decently well (though intense running might be pushing it).
Sound quality? It's... okay. Don't expect Bose-level audio here. At moderate volumes, music sounds clear enough, but crank it up and you'll notice some distortion. Phone calls work fine though - no complaints there.
Battery life has been surprisingly good in my experience - I consistently get about 8 hours per charge. The quick 2-hour recharge is nice too when you're in a pinch.
Now the downsides: The plastic does feel cheap (because it is), and the fit isn't perfect for everyone. Some users report them falling out during activity. Also, durability seems hit or miss - mine are still working after 3 months, but others report failures around that time.
Bottom line: For $12-$20, these are decent budget earbuds for casual use. Just don't expect premium quality or longevity. Perfect for walking the dog or desk work, but serious athletes might want to invest more.