Brush Research Flex-Hone.
Used once, very flexible, and worked great. Much easier to use than the 3-stone. It is 89mm which is the correct size for the 84mm bore of the M20 and likely anything else in that vicinity. You want the hone to be larger than the bore.
$25 or trade of some sort... Might be interested in a non-worn-out M20 cam, headlight brackets or an iX power steering line.
