NGK's unique design directs the spark to the edge of the electrode where it can develop more rapidly. This allows easier and a more complete combustion of the air/fuel mixture. The increased ignitability allows the engine to burn air/fuel ratios that would otherwise be too lean.
For race built/prepped engines, a common problem with iridium or platnum plugs is that when the fuel ratio is rich on start up, which over a short period of time, tends to foul these plugs easily, thats why NGK copper core plugs works well. They are economically priced to replace, and feature a "not so sensitve tip". The brittle and sensitive tips featured on them are easily burnt off during hard driving or high boost and high compression environments.
Unlike the common NGK temp 7 copper plug that is gapped at .044, these plugs are gapped at .034, which is why we dubbed them "small gap". The smaller gap is more suited for higher performance motors.
In a nutshell, the NGK temp 7 "small gap" copper race plugs are the best all around performance plugs for your "all motor" or "mild" forced induction motors.