The arch height of decoration is not less than 2.2 meters and not more than 2.5 meters, and the minimum is about 1.2 meters. According to the specifications of the arch produced by the gas mold factory, the following description is made: after blowing up at 8 meters, the distance between the legs is 8 meters and the outer diameter is 8 meters. The diameter of the 8-meter arch is generally 80cm, so the inner diameter of the 8-meter arch is 6.4 meters.