First, my apologies for not replying quicker. No excuse. Sorry.
No, Bonsai Block is not the same thing the same as turface ... perhaps made in a similar fashion, but to see the difference go to BonsaiJack.com. I use it for all the same purposes as described for turface and pumice, but it has a little more weight, which CAN be important for columnar cacti that are tall enough to want to tip over a pot. So I use something heavier than, but IN ADDITION TO, pumice. Bonsai Block does not have the surface features that pumice does and therefore lacks some of the water retention properties.
Available in 1/4" size pieces ... prices TODAY are ...
2 qts $15.65
1 Gal $19.95
2 Gal $24.22
3.5 Gal $30.87
We call it turface, BonsaiJack.com calls it Monto Clay ... available from a LARGE variety of sources, I won't go into prices. Same thing Pumice.
I'm a BIG proponent of Bonsai Block, Pumice, Turface, and use them ALL along with a number of other gritty non-organic components. I also include a small percentage (10-15%) of Douglas Fir pine bark fines, as cacti roots quite apparently LOVE them, and cling to them with a ferocious tenacity. If the cacti cling to the bark fines with such a determined, ravenous, unshakable fashion then there MUST be something to them that the cacti either WANTS or NEEDS.