The largest model in the heavy duty series is the JS490HDW which is the ideal size is for scuba divers and rescue teams. Because the HD is spacious and stable this enables it to transport heavy equipment like scuba gear. The heavy duty is designed to operate with a four-stroke engine, which can often weigh 40% more than their two stroke predecessors. All HD models are light enough for 2 people to carry and small enough to still fit in a car.