This is the nucleus and spring / solenoid plunger for use on black solenoid 33013. The correct part number for this is 33229. Some early CB 500 manuals have this part erroneously listed as 33226. Found in burners CB 500, CB 525, CB 525 S, CB 550, CB 90 HS, CB 85 HS, CB 90 HPB-AIR.