The Flipstone sharpening stone is an automatically folding sharpening stone that can be used on two sides. The dimensions could be compared to the ones of a pocket knife. The FS3 is just slightly smaller than the FS4. You can therefore always carry this sharpening stone with you. The yellow side is a diamond sharpening stone with a grit size of 25 microns. Repairing the cut is done with this side while the maximum sharpness is determined with the ceramic side of the sharpening stone. Both sharpening stones are glued together and will not come loose.
Although the sharpening stones are obviously harmless, they can be locked in both folded and unfolded position.
Such as is often the case with diamond sharpening stones, the surface has to be 'worn in'. Only after sharpening approximately 10 knives it will have acquired its definitive sharpening features.