My orignal one came off a 91tt. The solenoid is 2' long. the top pipe T piece where the hoses connect to can be removed by removal of a single phillips screw, and the adjusting screw has a rubber seal prior to the threads. I have another which has a 1.5" long solenoid, the T-pipe is not removal and the screw has a o-ring after the threads on the shaft. Why are they different and can they be interchanged. The last one did come from an NA motor so are they TT and NA specific?