Grivel Black Hole 5-Pack Fall 2009 The Black Hole by Grivel ice screw protection. Good protection for the sharp and delicate tips of ice screws during transport. New design that fits various diameters of screws. The bottom of each cap is pierced to release any water and dampness that could cause rust, a problem with the old caps. Whilst using the screws the protection can be hooked onto the screws handle where it doesnt risk being lost. This is a solution to two problems: rust on the blades of screws and losing the caps whilst out. Patented.