power limiter board ?
 

check this link out its about a circuit board u wire in between the battery and esc to limit power my views on this item are on the page richard ludlam and then richard again lol
let me know what you think and if its really needed

http://www.redrc.net/2013/01/c-andys...#comment-81927

In the uk it's a waste of time.
In the US, where there are different classes for the sake of different classes it is potentially huge