FLY HIGH Ball Tilt Maze for iPhone4 and iPhone4s.
Designed to work with ball bearing up to 4mm in diameter, but 3.5 works best with FLY HIGH Ball Tilt Maze Inserts. Features slide groove for a cover, so you don't lose your ball.
~ 2.5mm ball bearing (you can get these for free at any bike shop)
~ Plastic Screen (this can be any screen cover or clear plastic cut to size)