Our aluminum sprinkler risers are available as: Threaded on One End and Threaded on Both Ends.  Risers Threaded on One End are used with Webstermatic Quick Couplers.  Riser that are Threaded on Both Ends will thread directly into the sprinkler coupler.  Riser height is usually determined by the crop's height.  Ideally, the sprinkler's stream  should just clear the adjacents crops.  The taller the sprinkler riser, the more likely it will be an impediment to spraying.