The "slot" drive oil pump has been the factory standard for many years. The evolution of the pump in production was started with the "pin" drive that is most common in early small bore motors. These pumps have a fork on the drive side to engage the "pin" in the end of the camshaft. Many 1275cc engines were then given "star" drive pumps. The pump has a splined shaft that engages a "star" drive that fits into the camshaft. The latest slot drive pump has a screwdriver end that engages a "slot" on the end of the camshaft.