Review on 6" X 18" A Grade Granite Surface Plate - Perfect For Precision Measurement! by Loud Forrest

I haven't confirmed the flatness, but I'm impressed that a flatness map was included. If it's as flat as the map claimed, this is an amazing tool and value. For serving as a backing plate for straight razor servicing, the plate is a universe better than what I've seen a YouTube expert advise, which was a granite tile from Home Depot for $6. That surface (I tried two) was ridiculously warped compared to this plate. On this plate, any variation from flat is far less than what I can detect. I'm very happy and it shipped in a wooden crate.