When you purchase this key, you get to choose which of the 7 items you want. This is not luck based.

In the server, you can choose one of these:
Damage Booster
Money Booster
Shards Booster
Points Booster
Spawner Loot Booster
Spawner Speed Booster
Spawner XP Booster

The Boosters provide powerful temporary enhancements that can significantly increase your abilities in the game.