1.When a bike is intended to be stolen,loudly alarm will be issued. 2.Safe and reliable 4 digital codes electronic lock. 3.high sensitivity;3 level for sensitivity adjustment. 4.Rechargeable lithium battery,>6 month using life(20 alarms/day),easy charge,never take out the battery. 5.Reset key to avoid forget your code,easy use. 6.Alarm sound:>120db. 7.Power:3.6V rechargeable lithium battery*1pcs