The Boyer Bransden MKIV is a contactless ignition-triggering system featuring an electronic advance and retard. Designed to fit all British unit-construction singles and twins, this system is powered by your Lucas-style stator. Twins require two 6v coils wired in series, while the Singles take a 12v coil. The Boyer also retains the original capacitor, rectifier and zener diode, all three of which can be replaced by a single unit, the solid-state Sparx box. The MkIV is the best Boyer choice for off-road, battery-less use. Special order, takes two days.