Upgrade your KeyBackPack to open 600 more keys at a time.

Stackable: YES
Max Level: 120

Level 1: +5 Keys (25 Total without a rank)
Level 2: +10 Keys (30 Total without a rank)
Level 3: +15 Keys (35 Total without a rank)
Level 4: +20 Keys (40 Total without a rank)
Level 5: +25 Keys (45 Total without a rank)
...