They offer:

Dual steel ball-bearing locking protects shackles against pulling and prying. solid, iron-shackle shrouds on high-security padlocks make them virtually impossible to attack with bolt cutters.

Shackles of extra-tough, hardened, boron-alloy steel provide up to 15,000 lbs. of resistance to cutting and sawing, more than twice that of standard steel shackles.

Cylinders with special spool pins make padlocks almost pick-proof.

Pro Series padlocks are protected with tough thermoplastic covers and feature flow-through debris channels that keep dust, dirt and other contaminants from jamming the lock mechanisms.

Master Lock Pro Series are compatible with Best and Best-compatible interchangeable cores; Medeco high-security cylinders and numerous commercial door hardware cylinders, including Master door hardware, Schlage C through L, Arrow, Weiser-Falcon, Kwikset, Bilock and Yale #8.