drilled hard porcelain stoneware. I don't know the Pei rating but I think it was a 2 or 3. Starting the hole was a little risky but with the advice of another review I drilled a hole large enough for a drill length of the block of wood and held it to start the hole where I wanted. Walking got better. I can't comment on their lifespan due to the price and used a new drill bit for each hole to minimize risk, but I think it could have been done with more than one. He kept spouting water, oftenโฆ