What it does is slows the oil flow thru the shock as you increase in numbers which dampens movement of the shock, very similar to using different weight oils in your front forks. Higher weight oils (thicker) flow slower thru the fork valving so dampen more, lower weight oils are thinner so dampen less = same principle as adjusting the Dampener only the dampener works thru valving/orvice change . In other words it makes the shock more of a slower shock at higher numbers. I am not sure if it works both compression and rebound but I have a hunch that it does just by the feel I get when riding 2 up and fully loaded and my MK1's. Each "click" upward or downward is quite noticable on mine BUT, it does not add support of weight, that is basically Spring tension and Air Pressure. I run 70 pounds of air in my rear MK1 mono's so it is at full weight support. Then adjust my dampener as needed. Way to check? With bike suspention warmed by riding it some, centered and off stands so the suspention is carring the weight of the bike, put the damper on 1 and bounce on the seat and feel the rear shock movement. Now put it on 4 and do the same thing, you should notice a pretty good difference in how the shock dampens/responds. Also remember that the damper nob adjustment will not change ride height or weight carrying ability. If you let the air out of the rear shock, bounce on it a couple times and put it on the side stand and then push 70 psi of air in it you will see the bike actually rise, thats because adding air actually works like increasing spring tension. Ok, you got my opinion,, hope it helps lol