Rain Bird 21171401 Top Serviceable Rock Screen and Valve Seat for 500 and 700 Series Rotors - This Top Serviceable Rock Screen and Valve Seat is for use with Rain Bird 500, 550. 551, 700 and 751 Series Rotors. Made for easy installation and use, these parts will help ensure the best service life possible. Rain Bird rotors are engineered to deliver a low precipitation rate, so you can cover more area over a longer period of time.