Killark VR641C3 - Patented “Breech-Lock” cap serves as both flip lid and screw cover. Patented notch in cap arm holds cap open for easy plug insertion or maintenance. Type 4X rating when inserted into VersaMate receptacle and locking ring is tightened.Patented pin design uses slotted spring clip which avoids excessive wear while providing continuous electrical pin to sleeve contact. “Increased Safety” type box terminals with gripper ribs securely clamp around conductors. Boxes come with a green grounding screw.