3a thread class, right-hand thread direction, 0.563 inches minimum and 0.625 inches maximum thread length, 0.594 inches minimum and 0.625 inches maximum fastener length, fillister head style, 0.221 inches minimum and 0.226 inches maximum head diameter

An externally threaded fastener whose threaded portion is of one nominal diameter, no 0 (0.060 in./1.5 mm) or larger, designed to be held or driven with either a wrench or an inserted driver or both (excluding internal socket or internal multiple spline types), in sizes below no. 10 (0.190 in./5 mm). No. 10 and larger sizes must have a head designed for any type inserted driver (excluding internal socket or internal multiple spline types), but may also be designed for external wrenching. A locking feature may be incorporated in the design of the head or threads. Excludes:bolt, clevis; bolt, externally relieved body; screw, externally relieved body; and screw, assembled washer. See also, screw, instrument; bolt, machine; bolt, internal wrenching; and screw, cap socket head.