I have heard it describe as an artificial stone used to make countertops. They are a bit tedious to use because you need to lube them or the plastic sticks to them. They are descent molds, I have a few. They seem to dent easier as well as prone to flashing. the material is relatively soft as I have shaved off some of the ribs that were preventing complete pours. If you are looking for that style of bait then I would highly suggest looking into the do-it essential ripper. My 3.5 inch (3 cavity mold) is a walleye slayer. I gave some to some friends and they have reported 4+ pound smallmouth with it. The only downside to the do-it is that its not oriented for duel injector laminates. Also, do-it now has a 3" version (5 cavity) now.
The other concern with the ones in your link is that those are shipped from the Ukraine where there is a lot of political and military unrest right now. Shipping usually takes about 30 days from them. I currently have an order with them from about a week ago. I am hoping they come through. I have ordered from him twice before and he is reliable. I am just worried about them being caught in red tape because of their political climate. His aluminum molds are pretty good although I have had some problems with his alignment pins loosening up on both the artificial stone and aluminum molds. one other note- UPS wont deliver them without a signature on the customs forms.
Good luck-