of the drawing onto both faces of this film base were coated a dispersion of acicular cobalt modified gamma fe 2 o 3 particles in a polyurethane binder containing an isocyanate curing agent the acicular particles had a median length of 0 2 micrometers and an aspect ratio of 4 1 the coatings were dried to thicknesses of about 1 4 micrometers to provide a magnetic recording medium into both extruders used in example 1 was fed a mixture of 100 parts of polyethylene terephthalate and 3 4 parts of a 70 30 mixture of carbon black masterbatches a and b coextrusion as in example 1 provided a single layer polyester sheet which was biaxially oriented and heat set as in example 1 to provide a polyester film base about 0 075 mm in thickness a face of this film base is shown in fig3 both faces of this film base were coated as in example 1 to provide a magnetic recording medium each of the magnetic recording media of examples 1 and 2 was punched burnished and assembled into a diskette jacket to provide diskettes 1 and 2 respectively each was tested in comparison to two other diskettes which were made in the same way except with different film bases a 34 control 34 diskette had a polyester film base filled only with 0 2 by weight of calcium carbonate slip agent having a median particle size of.