1" (25mm) Flex-Hone Cylinder Hone Tool 400 Grit (Aluminum Oxide) Designed to work with cylinder bores from 0.9500" to 1.050" or 24mm to 26.5mm. Perfect for all engine types and block materials. EXCELLENT for reringing jobs or final bore for bores electropolated with a Nikasil coating. Tool is labeled as 1.000" diameter but is actually slight;y larger to apply the required wall force for honing a 1" bore Made in USA by the one of the best cylinder hone manufacturers, FLEX-HONE.