NGK ES and ECS spark plugs may have identical specifications when it comes to shell dimensions. However, ECS plugs have a special low-angle ground electrode design. Low angled ground electrodes are shorter and closer to the metal shell and center electrode, providing a faster path to transfer heat away from the ground electrode. The low profile design is also resistant to vibration, making it ideal for use in powersport applications.
Many 2002+ SkiDoo snowmobiles come factory equipped with NGK ECS spark plugs. Failure to use the recommended ECS plug may cause failure of the ground electrode, resulting in costly engine damage.