My integral compensators are machined out of stubs of barrel-blanks. They start out 1-1/2" long and are internally bored and threaded. After screwing them onto the barrel, you end up with about 3/4" longer than the barrel without the compensator. In other words, a 20" barrel is 20-3/4" finished length with the compensator.
They are incredibly effective! I built the first one for my young son that complained that he couldn't see the hits/misses on prairie dogs. Being his was a "Bull" profiled barrel, there really wasn't anything available that would work. I spent hours on the first one, but have gotten it down to where I can actually make shop rate on them.
They are only ported straight up, so to the shooter, there is no difference in report. If you are shooting from a covered firing position, or if the shooter is in the prone position and there is someone standing beside them, then you will hear and feel the blast. Shooting in the field you will never know the difference, other than you will see your hits.