Set of 6 x string insert clamp block for Schaller, Floyd Rose and most common locking tremolo systems. If you've never lost one of these when changing strings or doing other maintenance, then you're truly a blessed individual. Your luck WILL run out one day.
Then you can join the rest of us in searching all over the floor looking for those pesky little blocks, but they never get found. Enter your spares!
Perhaps the single most important spare part for users of Floyd Rose style tremolos. Buy a bunch and never have to crawl around on the floor for half an hour just to turn up nothing.
Genuine Schaller Germany part.