This thing is great, I haven't put in the head piece yet but fit for the chest piece is AMAZING you can adjust the fit so that it sits above the chest really comfortably, and it sits really tightly. It IS NOT WOBBLY, you just have to adjust it correctly, I am a big big person and you don't have to wear it centered in mid chest, you can pull it up and wear it at the top on your clavical, it is sturdy and once you get it just right, you can unclip it to remove it so you get to keep the exact fit!
I LOVE THIS THING! I recommend it definitely, I use it for walking my dog, and it's so sturdy and good for a great amount of hiking and activities.
I'm extremely impressed especially for such a low price.