The Personal Chest is a storage block added by Mekanism. It can hold 54 stacks of items (the same as a vanilla double Chest) and adds 3 modes[clarify]:
Public: Everyone can open the Chest and take its contents. It the only mode that allows automation with redstone devices and/or item pipes.
Private: Only the player who crafted the chest (the owner) can open it.
Trusted: The owner can choose who can open the chest.