 sort of breakaway plastic risers that have a notch built into them. If they get hit by a lawnmower, instead of breaking the underground piping, it breaks the riser off, and you can replace it very easily. So I have to do... You might check to see if some of your heads are below the natural ground level, and that way you're not getting the coverage that you would like. A dead giveaway, by the way, this time of year. It's not...