LATCHING PUSH BUTTON SWITCH: Push it to ON mode, Push it again to OFF mode. Easy to operate and use. BLUE LED BUTTON LIGHT: LED light can be on all the time or only on when switch is in on mode, depending on how you wire it. ALUMINIUM ALLOY SHELL: Durable enough for long time use up to 500,000 cycles. ???Note: Mounting Hole Size: 16mm. EASY INSTALLATION: Round latching switch with screw clamp type terminals make installation easier. WIDE APPLICATION: This 12V push button switch is suitable for Marine, automotive and aircraft control panels.