Underground System Installation Guide (PDF)
When I had my sprinklers install, I requested that they be low enough to allow a lawn mower to pass over them. This they did not do, and it was very difficult not to hit them. It then took time to dig them up and replace the fitting. I tried digging along the pipe to lower them, but the head returned to it's original position.
I found your "Multi-Flex riser" at Lowe's and added two right angle fittings. I dug down around the existing sprinkler head to expose the pipe. Your Multi-Flex riser, with the addition of right angle termination, allows the sprinkler head to be lowered to a flush position with the ground.
I have so far modified a dozen like this in my back yoar. They work very well and solve a difficult problem. I have another ½ dozen to go and wanted you to know my pleasure with your product.