Backing material (not wood) for 2000 Air Warrior seats?

[Reefboy 0]

I have a seat that the main support/backing is broken.  It appears to be a grey material and not really wood.  Is this a common material from the early 2000's?  What is it called? I would like to have a few seats reupholstered and would like to have this replaced at that time..

Thanks

[Tallredrider 3]

I would use King Starboard.  It is durable and waterproof.  Easy to cut to size.