The thick silicone protection is 1 to 2 mm, covers the power and volume buttons (no problem to use), and openings (camera, USB, etc.) if they are not adjusted to the micron pose no particular problems.
The matter in hand is nice, but a bit slippery (it might happen after a while). As against the burrs (product injected) are only very coarsely chopped.
If you are looking to protect your phone cheaply, this is definitely the kit you need.