10Pcs Black KW12-B Micro Lever Arm Normally Open Close Limit Switches, with Lever. Working principle: By external mechanical force transmission elements (by pins, buttons, levers, rollers, etc.) will be used to force action on a reed, producing reed instantaneous action when action shifted to the critical point, so moving contact with the fixed contact spring at the end of the action point fast on or off.When the force is removed on the drive components, action reed produce reverse action force transmission element reverse stroke when the action reaches a critical point reed, instantaneous reverse action. Package included： 10* KW12-B Micro Lever Arm Limit Switches