See if you can get the part number from the shocks in question, here is a list of air shock part numbers and lengths.
In my opinion the air shocks will give a way better ride than the 11" 412's you have now, for $20.00 it's a no brainer to at least try them.
54532-85
54536-02A
54540-93
54565-09 FLH FLHT FLHR FLHTI 13" (G5E3-00)
54565-97 (A) FLH 13"
54565-97 (B)
54565-97 (C)
54631-02B Road king FLHRS or FLHX or FLTRX 12" shock pair "low profile"
54632-98 bagger 12" or 12.5
54635-09 12"
54661-02A Road King FLHR Street Glide 12" single shock "lowered"
54662-09 street glide 11.5"

 

 

These "air" shocks require very little air, I run mine with 0 PSI for one up and about 5 PSI if I have a passenger.
I seldom have a passenger so I don't have to change the air pressure very often so I just picked up two schrader valves for the air holes in the shock and a use a small bicycle air pump and use an air pressure gauge from a quad (the only kind that is accurate in the 0-10 PSI range).
DO NOT grab a normal air hose and put 50-100 PSI in these shocks you will wreck them, the compact bicycle air pump only needs one or two strokes to go from 0 to 10 PSI so your dealing with very small quantities of air at very low pressure.
Keep in mind this is not "air ride", the air isn't supporting the bike it only adjusts the internal valving for the amount of compression and rebound resistance, adding air will not lift the bike or allow it to carry more weight.
You can add hoses and an air compressor to the bike if you want but it's not necessary at all.

 

check post #659 on this thread.....
https://www.hdforums.com/forum/sport...l#post15398157

schrader valve with HD air pump which does not release pressure when removing the pump from the valve
https://www.harley-davidson.com/stor...nsion-air-pump

Good ride,...you can always adjust the PSI for the weight your carry. IMO would be better than the 11" progressives.

 

I've got RK shocks on my (much) older bike. 12" is I remember correctly.
I run them with 0 psi and like them. I'm about 175 and never ride two-up.

Here's the point, if they're in good shape, they're worth risking a Jackson. You will probably never find a better deal than that.
I paid $50 for mine, and it was worth it considering how much decent shocks can cost.
If you don't like them, you could probably get your money back.

 

 

Be aware that these are air-over-oil shocks, not true "air spring" type shocks
like Legends or Arnott systems. The air pressure controls the oil through
a valve rate. Do some searching & you'll find a few threads on how to
drain & replace the oil before you install them.

good luck,

T.

 

Try to find some 12" street glide take off's. I've been really happy with the ones I found. I drained and refilled the shock oil and installed two Schrader valves as mentioned above. I found two pumps with a bicycle hand pump gives me the nicest ride. I knew I wasn't going to be happy with the look of the 13" shock, the 12" ride height is perfect, gone are the days of bottoming out over potholes and scraping bottom over speed bumps.

 

Those shocks are actually metric in length, so are approximately 12" or a little under 13" overall in length. The longer ones have significantly more travel, so in theory should provide better comfort.