Depends on your power and the tire you're running. Strange rear double adjustables are a good price and work pretty well up until a certain ET... normally anything slower than 5.80's in the 1/8 or so we use Strange. And we usually use AFCO's on cars quicker than that... again to a certain point (and we have a custom TRZ valved AFCO for a drag radial tire). Menscer valved AFCO's are a little more pricey and we generally try and use those on 5.0 cars and quicker (in the 1/8). If it's just a 6.50 car or so and on a slick, you can get by with a Strange single adjustable... for instance.