the like to the mandrel surface by a suitable binder such as an epoxy resin thus as shown in fig3 the surface 26 is coated with epoxy resin 19 having particles of sand 21 mixed within or added thereto and allowing the epoxy to harden so as to provide a sandpaper like roughness to indent the elastomer of the sleeve 14 as at 23 and to cause the sleeve to move vertically with mandrel 12 and to thereby prevent damage to the upper portion of sleeve 14 or to ribs 17 during the manufacture of the packer the sleeve may be laid up on the mandrel and then cured in place to avoid the rubber bonding to the gritted coating a suitable mold release agent such as a powdered limestone aqueous paste can be applied to the mandrel coating this coating after the rubber is cured can be removed by a suitable solvent e g hcl acid wash followed by neutralization of any residual acid by a suitable base such as sodium bicarbonate heretofore grit coatings described above have been applied to the outer surface of casing strings in an attempt to improve the cement bond with the casing however the grit coating is exposed to drilling mud when the casing is run into the well and becomes impregnated with a mud cake which prevents good contact between the grit coating and the cement with the instant invention the rubber sleeve extends around the grit coated mandrel and isolates it from the mud in the well accordingly when the packer is inflated with.