The HS2T3ZZV is a 2 Water Delivery Temperature, 3 Zone by Zone Valves Zone Panel. This panel can be used with The HSPS120MZH, HSPS190MZH, HSPS150MZH-HTP, or the HSBP6W-HS115-MZH integrator panels. This panel is desinged to be used when you have two different emitter types that reqire two different water deliver temperatures. For example, tubing in concrete should never go above 130° while baseboard usually requires 145°-160°. If you had both of these emitters, you would need a 2 Temp Panel.