None,
Except one time got hit direct center of it and it popped open.
Review:
Ok when i first got this hopper, i at first thought the body was a little akward, but then i got used to it and just love it now.
I have changed the batteries 2 times only using 1 9 volt each time, and played 4 woodsball games.
The hopper also catches bounces, so i was told when playin by the ref.
Conclusion:
Go buy one, i got it new for $70 ansgear.com Great hopper
