D4E Coolant-Resistant Limit Switch Omron Industrial Automation D4E Coolant-Resistant Limit Switch is oil-resistant and designed to meet needs in applications such as machine tools, processing machines, and the manufacturing of automotive parts. An Omron-developed rubber seal dramatically increases the durability against coolant exposure. The durability of this coolant-resistant model is 4 times longer than the standard model. The switch comes pre-wired with an M12, 4-pin connector on a 0.3-meter cable which allows for quick and correct connection saving customers' maintenance cost.