Abstract: There is disclosed an improved fastener and driver assembly which assures sufficient depth of engagement between the drive socket of the fastener and the working portion of the driver bit to provide efficient torque transfer from the driver to the fastener. The assembly includes a fastener having a recessed drive socket which is multi-lobular in cross-section, having an inner surface formed by alternating and smoothly joined flutes and lobes. The assembly also includes a driver for imparting rotational torque to the fastener which includes a head portion having a tip end and a center axis. The head portion of the driver is correspondingly multi-lobular in cross-section. The flutes are formed generally parallel to the center axis of the driver while the lobes of the head portion are tapered axially, converging toward the tip end of the head portion.