First choice of Hotels. Double composite lock structure, sturdy ,durable and reliable; U.S. standard lock B mortise, Simplicity by making of only 20 parts inside the lock mortise, flexible, higher reliability; Anti-plug design, and combination latch bolt abnormal alarming design combined; Double guarantee, double safety, Computer board adopts imported electronic components, automatically SMT (Surface Mount) process, Australia mildew protection surface, stable and reliable quality