This padlock, manufactured by Master Lock, is used to secure the Extreme Blue timeclock to its mounting plate. The user sets the lock to one of 10,000 possible four-digit combinations of 0 through 9. The hardened steel shackle and 2-inch metal body discourage theft of your Extreme Blue system. Also compatible with TimePilot Extreme, which has been discontinued and replaced by TimePilot Extreme Blue.