UPDATE
I dislike the 3500 rotors...I used 17 of them on a job last week and hate the way they adjust, hate the way the spray pattern works in other than fully open position...and hate the way it is easy to break the adjustment screw.
If you haven't bought them already, go with the PGJ...sorry for the poor info.
Sprinkler Solutions, Inc.
Arizona and Colorado
www.sprinklersolutions.net