Last Sunday I noticed a crack in the top corner stone of my new Keystone. Never dropped anything on it or overfired so I don't know what happened. Monday I emailed Woodstock some pics and that day they sent out a new stone with replacement instructions. Taking the top off was only 2ea 1/2" bolts right next to the cat they the top just lifts off. Another frame holds the stones in place and there are many gaskets underneath which I think is a good thing so I didn't have to mess with any cement. Gaskets were all good and replacing the stone took about 1/2 hour. Thanks to Woodstock for such quick warranty service with no charge to me.