Sleeve refers to the abbreviation of socket wrench, and the big fly and small fly of sleeve are divided according to the size of the square head of socket wrench. Generally speaking, 1/4, 3/8 and 1/2 refer to the side length of the square joint on the socket wrench, 1/4 refers to the square head size of 6.3MM, 3/8 refers to 9.5MM, and 1/2 refers to12.

Engine torque limitation means that the torque output of the engine is limited, which can be understood as power limitation.