This heat is why press temperature control systems are required to allow for the precise control of temperature within the printing unit. The most popular systems use vibrator cooling, in which coolant is pumped through hollow core vibrator rollers in the inker. This type of system has been in use in high speed web presses for many years. The technology has been refined and is now being applied to sheetfed equipment as well. Almost all sheetfed press manufacturers offer hollow core ink vibrators which can then accept the after-market temperature control systems.