I found out about it with my 350 chebby boat. Then told some friends, they put it in 2 cycle engines, and raved. It used to cost $4; now that everybody knows about it, price tripled.
I hear the re-ring/valve job pills you get in the JC whitney catalogue, along with the bearing restore you can get there works wonders too! Just like the prolong makes your engine last forever and silents knocks!