[SSDiv6]

Although Hard Blok claims the expansion rate of their product is the same as gray cast iron, when I spoke to them, they could not tell me how they based their claim.

On the other hand, Embecco 885 is a fully tested product for use by the government, with lots of supporting data and it contains cast iron in its formulation. Never had any issues with the product and the blocks have never changes in the block dimensions.