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Just as comment on the stronger spring. I replaced the guts on a 570 Toro recently with the new design and it wouldn't pop up. Upon further investigation I noticed the spring was much stronger. Had to swap springs. I've had that problem swapping from an 1800 to a SAM as well. If you have good water pressure I wouldn't worry about the I20's. Boots is right. The I20 is a good sprinkler. If the extra cost isn't a factor the I20 will make you happy.