Whats the diff between the single and double adjustable? I know doubles have settings for the rebound and compression I think so does the single just have rebound?

 

The singles don't independent allow you to adjust rebound and compression, one setting sets both parameters. In drag racing you want to "loosen up" rebound but keep your compression stiffer, can't do this with single adjustables.

 

what about the rear, doe it make a diff? I ask because someone is selling some double adj rears but eh rebound broke the setting 10 so I was wondering are they worth getting