The spiral on felt listed below is 100% Polyester. It is 3" (76mm) Wide and approximately 1/4" (7mm) thick. It is recommended for use on doffer rolls only. To calculate footage required, multiply 0.1833 x roll length in inches x half of the roll diameter in inches and then round up to the nearest whole foot. For example, a 3-1/2" diameter, 120" long roll needs: 0.1833 x 120 x 1.75 = 38.5 or 39 feet.