O.S. glow plugs have always been tough enough to take the heat — and Speed P3 and P4 Gold Turbo Plugs with 24K gold plating take O.S. innovation to new levels! They’re the perfect complement for .18-.28 cu. in. turbo head off-road racing engines. Even more important, Speed P3 and P4 plugs boast many performance upgrades like being easier to tune, more low-mid range power, faster acceleration and more.