It's a bear spray safety that says version 4 partially because that sounds cool. It's designed with a very tight grip so it never falls off, but I recommend taking it on and off once or twice just to make sure it will come off if you need it to. 0.2 is a good layer height, and you will obviously get a better grip the smaller your layer height is. If you can, you should probably print it in ABS just so it "survives the elements", not partially melting.