1.75" and as indicated by the two words at the top of this item "Keep Sharp" this was once a celluloid covered knife sharpening stone but the stone is missing from the underside. In addition the underside has .75" dented segment of the collet with its edge not quite seated correctly beneath the celluloid curl of the button but not really causing any problem in terms of remaining intact. Front of the piece is somewhat flattened on the left side but only a couple of very tiny indent marks in the celluloid which remains totally clean. No maker's name but among the very earliest farm equipment advertising oil stones. Still displays VF.