Originally Posted by wingracer

As others are saying, 99 is going to be too cold for most offroad applications. Maybe OK if your running high nitro or high compression or a heavily modded mill on a long track but generally you are going to want something hotter like a 97 or 77.

As for quality, they are good and run well for the price. There are better plugs out there but they all cost more. But then, if the more expensive plug also lasts longer, which one is really cheaper?