The Craftsman Exclusive 550ex Gold Series™ engine that was designed to provide an improved mowing experience for entry-level mowers. With a best-in-class torque-to-weight ratio, reduced vibration levels, and improved sound level. These engines offer features for hassle-free lawn mowing Smooth Start™ (Craftsman Exclusive) – Two advanced engine features combine to give you an easier starting engine the Most Reliable Starting (MRS) Spark Plug and the Advanced Ignition Coil. ReadyStart® – No priming. No choking. Just pull for power.