High quality material: The spring of the engine speed controller is made of high quality stainless steel, which is corrosion resistant, wear resistant, well done, without burrs and easy to install. Spare parts for adjustment spring: The package contains 4 replacement regulatory springs in two sizes. The amount is sufficient to change the original pieces (6.7 * 0.6 cm) and adjustment springs (4.4 * 0.3 cm). Excellent performance: the regulator spring has good elasticity and durability even after innumerable repeated stretching. The regulator spring is used in most engines to reduce engine noise and energy consumption. Improve machine work efficiency.