Patented keyless lock: 1. Heavy Duty: 2.3mm faceplate; +2.0 for internal parts 2. 660,000 combinations available 3. 6 digit codes: Must be sequentially pressed 4. Anti-peeking: press random keys before pressing correct code. Or, pressing correct code followed by any of the pressed correct code. 5. Anti-sensable keypads: correct keys have no conspicuous sensable feeling by hand.