A Super B with a 52" mulch/rear discharge deck 6 or 7 inch grass is no problem. I have cut 18" grass before with the 42" mulch deck before but it took several passes to make it look right. I amazed my helpers when I did it. They were ready to go to town on this overgrown property with the SD walkbehinds and make a big mess when I told them to stand aside and watch (ie start trimming) while I eat it up with the walker. They said i couldn't do it and I must admit I was a bit surprised too. Definitely did a better job than letting it fly and just about as fast because the was no clean up or raking. Mulching works! You just have to understand how a mulching deck operates and train your guys how to do it. After as much rain we had in 2011 and we mulched everything with no problem... I'm sold!