I tried the springfield one, the piston is not stainless and the sucker was rusting within a week. Sent that back for a refund.
I also checked out the Ridesoftly (
shock absorbing marine seat pedestal post) model, but the 22" height is too high for our boat (we have 16" pedestal) The unit itself was very well made though and I'd recommend it. At $295 thats a good deal too.
There is a similar unit by
Seaspension Shock-Mitigating Systems for Boats - Largo, Florida but that's more expensive at around $700.
The cadilac seems to be the model made by
Glyde-Ryde but again this is around $650, though its all stainless construction. It is in use by the Coast Guard, so that tells you something.
So there you have it. Good luck and email me back if you find anything else as I'm still looking too. There are other products besides the ones I've noted, but most of them are crap.