With transfer molding, raw rubber material is placed in the "transfer pot" reservoir. Then a hydraulically actuated ram forces the rubber material into heated mold cavities through consecutive sprues. The mold supplies enough heat for vulcanization as well as the process of forcing a viscous liquid (the rubber) through small passages. The result is a highly viscous hot compound that flows easily and cures rapidly, which increases molding efficiency. Since the rubber is forced into a closed mold, the resulting flash is far less significant than in compression molding. Transfer molds are more complex than compression molds, so they incur substantially higher mold costs. Additionally, transfer molding generally produces more material waste. However, often transfer molds can be run in the same hydraulic presses utilized for compression molding. High Performance Seals commonly uses the transfer molding process when bonding rubber to metal.