Sold me a grout that stated specifically it wasn't recommended for use with marble tile. Unfortunately, they'd sold me marble tile to go with it. If my contractor hadn't been paying attention, I would've lost a lot of money and set back my reno timeline. When I went to return the grout, the salesman actually argued with the manufacturer's specs - because he'd used the grout himself with no problems on marble tile, so it was fine. Guess the manufacturer just doesn't understand their product? And the poor service from the manager in trying to return the grout and unused tile? Unbelievable. Will never shop there again and will make sure everyone I know who has a reno project knows to avoid them.