Injection molding, where molten plastic is injected into a metal mold, is the most commonly used method in plastic mass production. The initial investment cost for making a mold is high, and it takes about one to three months. It requires a mechanical design suitable for injection molding, but it has the advantages of fast production speed, low part unit price, and mass production of complex structures with bosses/ribs. Injection molding up to 30-50K units is possible, and with a higher number of cavities, one mold can produce hundreds of thousands of parts.