Specifically designed for race applications, and the choice by more winning racers. Plugs for all popular racing applications. Give us a call with your application and we?ll get you set up today. General Guidelines For Heat Range Selection: Compression Ratio(9:1 -10:1; 10.5:1 - 12.5:1; 13.0:1 - 14.5:1; 15:1 - 16:1; 16:1 and Higher ), Recommended Heat Range(63 ? 65; 61 ? 63; 59- 61; 55 ? 57; 53 ? 55) For alcohol fuels, mild turbo or supercharged, and oval track racing (1/2 mile or longer) drop 1 heat range cooler. For nitrous oxide, severe turbo or supercharging, drop 2 or more heat ranges cooler. Smaller number = cooler. Prices are per each spark plug.