Fastener system with stabilizer ribs and square drive

A fastener, comprising:

• a head configured to engage a driver;
• a central recess core positioned in the head and having a recess bottom region;
• four recess surfaces defining four recess corners, the four recess surfaces extending from a top of the central recess core and connected to the recess bottom region and forming a bottom region transition edge at an intersection of the recess bottom region and the four recess surfaces, each pair of adjacent ones of the four recess surfaces meeting at one of the four recess corners such that the four recess surfaces conform to a shape of a square, the square having four corners coinciding with the four recess corners;
• and
• a groove in each of the four recess surfaces, each groove extending in a radially outward direction from a corresponding one of the four recess surfaces, each groove extending from a first distance from the bottom region transition edge to a second distance from the bottom region transition edge, the first distance being nonzero, the second distance being more than twice the first distance,
• wherein each of the four recess surfaces is flat from a bottom of the groove to the transition edge, and includes therebetween a recess interference surface, and wherein, for each of the four recess surfaces, the recess interference surface defines a design recess interference region located entirely below the groove and entirely above the recess bottom region.