Seat Upholsterer

I had an old Cutlass seat that the vinyl was perfect on it, no cracks but rock hard. I experimented in different sections with all of the aforementioned products, and even let it soak for months with no real progress. Most of the other forums basically said the same thing, if it's brittle it's too late. Now, I've brought back plenty of old leather on the other hand but that's a whole different conversation.
ya it depends on how far gone it is, as noted above... but it worked for me on an Arctic Cat seat. I wouldn't mention had it not worked.