This diaphram will work if it's a HydroRain. The horseshoe shaped solenoid was/is a mystery to me. You might have to swap out the rubber and use the existing plastic parts of the diaphragm. But from the picture it looks right. Or you can go to a local supply house and get the whole thing with new plastic. The part number might be, R1359. That picture looks exactly like the one I have in my hand. I have a brand new old stock HydroRain sitting here I took apart and a pack of HR1 diaphragms. They look compatible.
www.sprinklerwarehouse.com/Irritrol-SPK-HR1-Repair-Kit-Irritrol-Richdel-HR1-p/spk-hr1.htm
This post has been edited 1 times, last edit by "mrfixit" (Jun 13th 2010, 3:24pm)