Rain Bird Riser Bubblers screw onto 1/2 MPT pipe or risers. Available in adjustable flow designs and statitc flow designs which require no adjustment. flow rates range from .25 GPM to 2GPM. Bubblers can be installed on the end of a extension tube, cut-off riser or on the top of a spray body. Sprinkler Warehouse provides an extensive selection of bubbler for risers, pipe nipples or extensions.