This piston was used on some older (pre-2010) Water Soft softener control valves with an electronic Isobar control valve. 

Also used on softeners that were labeled "How To" or "H2Ow To". 

Only use this piston if your piston has a green cap as shown.

If your piston has an orange cap, you need the 20922C203

If your piston has a black cap, you need the 20562X254

If your piston has a White Cap, you need the 20561X254

Note: We recommend installing a new seal & spacer kit anytime a piston is being replaced.