"Austempering for improved product performance and a longer service life","Surface peening for greater durability","Lock-ring retention","Also includes a \"shot-blast\" process which relieves internal stress in the finished product for greater durability","Torx ends are formed rather than machined for a better match-up with fasteners and greater performance","Tri-Lobular Bit Retention - patented method of keeping bit secure in holder without movement 5/16" TAMPERPROOF TORX PLUS BTP45P | Matco Tools