they work well. much easier to make on the fly adjustments while you're running it in too easier to temp while ruinning in & you can control the process much better. they did a write up in RC car action last year, or the year before. there are ones made specifically for .21 buggy engines and pipes, it includes an L shaped header instead of the U shaped ones used on the buggy. if i had the spare cash i'd get one, instead i spend my money on tires & spares.