3-1/2" (89MM) Flex Hone 320 Grit Aluminum Oxide for all engine applications utilizing a 3.350" to 3.550"" or 85mm to 90mm Perfect for for all Nikasil coated or chrome plated engine cylinder blocks materials. with Nikasil Plated/Coated or Chrome Cylinder Walls. - Brand new sealed in package Aluminum Oxide engine cylinder flex-hone. Made in USA by the best cylinder hone manufacturer, FLEX-HONE.