|The material used for the base plates is a phenolic manufactured with cotton weave fabric (canvas). The particular grade is C , I used the 1/4" thickness (0.250) sheet.
Here is a web link with more detailed information including approximate cost.
I just googled Whale Tufnol and found what appears to be a brand name for this material that is manufactured by a company in the UK. So, I suppose it is the same thing? Although not exactly what I purchased. I got mine from a local plastics supplier. They usually only charge for the amount you needed and can cut the material to your required dimensions.
I did not weight the finished plates alone... sorry. I did weigh the entire setup though, and they are just a bit lighter than what I had before with the sure-gripe Super-X aluminum plates.