In order to correctly select which cover you need, go to the solenoid valves area and find the specific valve you have. You will also need to notice if your valve has Flo Control or not. The 205's and 2500 series valves have a large handle sticking up out of the middle of the valve cover that makes identification of flow control very easy, but the 2400 and 2600 series have only a small adjustment screw that looks something like a second bleed screw on the cover.

So, if your valve has a large turnable handle sticking up out of the middle of the valve cover, or if it has waht appears to be a second small bleed screw, it is a valve with flow control. If your valve has flow control, select the flow control version on the dropdown menu when ordering your cover.

Flow Control by the way, governs how quickly (or slowly) your valve opens and shuts. When water hammer or hydraulic ram is a potential problem because of high ambient water pressure in the area, a contractor will often use flow control solenoid valves in order to have the valve open and shut a little slower than normal in order to eliminate hydraulic ram or "water hammer".

Can a non-flow control cover be used on a flow control valve?  Yes, but you will no longer have flow control.

Can a flow control cover be put on a non-flow control valve? Yes, and you will then have flow control on that valve.