We use both a Supra Lock Box and a "Vendor" Lock Box on every one of our listings. We currently use the Master brand Vendor Lock Boxes - however - based on their website information, it appears that Lion Locks could well be a rival to Master locks: "Lion Locks' engineers innovatively created a top of the line lock that makes life convenient for the customer, impossible for the intruder. Lion Locks began with a basic lock built with the best quality materials and most secure locking systems. "