[CFster]

They're capped. What happens is sound waves come into the pipe, then are bounced back in an inverse pattern - which cancels out the noise. Reduces drone considerably. There is a formula to determine what length your j-pipes should be, based on what hertz range you're getting the loudest noise. An easier approach is to order these adjustable ones from Solo Performance. Then it was a little trial and error - loosen the clamps, slide them out 1/2", test drive, repeat.