Since 1976, practical "glow" ignition four stroke model engines have been available on the market, ranging in size from 3.5 cm upwards to 35 cm in single cylinder designs. Various twin and multi-cylinder glow ignition four stroke model engines are also available, echoing the appearance of full sized radial, inline and opposed cylinder aircraft powerplants. The multi-cylinder models can become enormous, such as the Saito five cylinder radial. They tend to be quieter in operation than two stroke engines, using smaller mufflers, and also use less fuel.