Aircooled VW South Africa

What is the best treatment for original seats on my 61 Beetle I am not sure what material they used at the factory.The car sits for long periods and there is no movement on the seats which is making them a bit brittle.
Could I use that food for leather.Any one got any ideas.

I've had good results with glycerine. It moisturises rubber and vinyl and brings it back to life and keeps it supple.

That is something I never tried thanks Fig. I was just worried about silicone as its petrolium based and could do more harm than good in the long term.