This tool makes measuring ring end gap faster, more accurate and eliminate the guess work Install tool into a cylinder bore and then view the ring end gap in the ôKey Slotö Flanged design allows piston ring to fit squarely in cylinder bore every time Each side of the tool is made for checking a standard size piston rings Just install any ring, top, 2nd, or oil control rails on the tool Use a feeler gauge to get your end gap measurement Made in the U.S.A.. TOOL PISTON RING GAP HD