Model Heat Range Description
- No.6 Hot Formerly known as the OS A3 plug. This hot plug will provide a more stable idle and crisp acceleration when compared to a cold plug. This plug is recommended for low nitro content fuels and .12 class engines.
- No.7 Medium Hot Slightly "hotter" than the #8 and ideal for the constant "on/off" throttle action in 1/10 and 1/8 scale racing.
- No.8 Medium A medium heat range plug for 1/8 scale racing and most .12-21 car, boat and truck engines.
- No.10 Cold Formerly known as the OS A5 plug. This is now rated as a cold plug and is recommended for high nitro content fuel. This cold plug will produce the most power, but will provide a less stable idle and a narrow tuning window
O.S. engine plugs are SHORT body plugs and should only be used in engines that require a short body plug. O.S. plugs should not be used in Novarossi, RB Concept and most other motors manufactured in Europe.