Denso Platinum TT spark plugs feature a twin-tip design, allowing for a more efficient combustion, which yields better engine performance in terms of power and fuel economy. 1.1mm platinum tipped center electrode and titanium-enhanced 1.1mm ground electrode. Machine rolled threads prevent seizing or cross threading during installation and removal. 100% pre-fired to assure the highest quality possible. Purified alumina powder insulator provides exceptional strength and thermal conductivity. Five rib insulator prevents flashover. Copper-glass seal bonds center electrode and insulator for a gas-tight seal.