Hard material on bottom side of Hot Springs tubs

[LukeJ]

I have nearly completed repairs and foaming of a leaky 2003 Hot Springs Soverign that came with our home.  The last step is to determine what the very hard shell material is on the bottom side of the tub.  I have roughly 8 sq. ft. taken off, and it looks to be about 1/10 of an inch thick.  Can anyone link me to a place that sells this material?

Thanks,
Luke

[TwinCitiesHotSpring]

there ya go!

http://www.backyardplus.com/proddetail.php?prod=70867

[LukeJ]

Thank you.   Wow! Expensive but worth it.