I recently purchased a Giffin Grip Jumbo Platter Extender and wish I had bought it back when Brian Giffin first invented it. It makes trimming large platters and bowls far easier than my makeshift attempts of the past. The largest bowl/platter I can fit in my kiln is 23" in diameter which is the largest piece that can be trimmed using this centering device. Actually, it is far more than a centering device. Just watch the video and you will know what I mean.