The Bostech DE621 Silver Series Remanufactured Fuel Injector for your 1987-1991 GM 6.2L Diesel are a direct replacement for your worn factory injectors. Mechanical Injectors open and close at predetermined pressures. Fuel is distributed in a near continuous spray that is injected into the cylinder. Although this technology has been around for a while, and doesn't seem to give near as many problems as the more efficient and modern common rail injector, they still wear over time and do fail. Each injector is remanufactured to Bostech's stringent quality control. Sold individually.