This Honeywell ML6984A4000 Motorized Valve Actuator is a self-controlled, self-adjusting, motorized linkage that mounts straight onto V5011 two-way or V5013 three-way valves and supplys up to 25 mm (1") of linear travel (stem lift). It is to be run with SPDI series 20 (on-off) and series 60 (floating control) 3 wire thermostats and controllers.