PATENT PENDING BLOCKGUARD ANTI-SHIM TECHNOLOGY WITHSTANDS ATTEMPTS TO VIOLATE THE LATCH MECHANISM. INCLUDES COMBINATION CHART TO FACILITATE LOCK SYSTEM ADMINISTRATION. 3/4"" (19MM) TALL HARDENED STEEL SHACKLE FOR EXTRA CUT RESISTANCE. EASY 3-NUMBER DIALING WITH AUTOMATIC SCRAMBLING FEATURE TO PREVENT REOPENING OF LOCK. ALL MASTER LOCK LOCKS ARE NOT RETURNABLE.