This coil is for use where a ballast resistor is used to aid starting. Whilst the starter is being operated the ballast is shorted out, giving the coil the full 12 volts. When the key is released the current is drawn through the ballast lowering the voltage by 2 or 3 volts. This coil is a direct replacement for the Lucas DLB102. The coil body is 55mm diameter and the coil tower is made from phenolic resin. Complete with fixing clip. (Not Lucas branded)