Plastic containers produced by this method like various bottles, square, round or flat barrels, gasoline tanks, etc. have been widely used. Besides, the various newly developed industrial parts and daily products have been applied in practice. E.g. double-walled box-shaped products, L-ring large drums, stacking boards, surfboards, seat backs and desks, as well as front spoilers for automobiles, belt covers, instrument panels, air conditioning ducts, etc.. And the processed materials are developed from daily-use plastics to engineering plastics. Nowaday, blow molding has become one of the important molding methods in plastic processing.