Wrench Set Flat Box End 6 pc N-PowerFit Drive- Increased strength and reduces rounding or fastener damage by distributing stress through a gentle arc in the bore by enlarging the contact surface. Double box ends with proprietary internal bore angle of 7 degree and 30 seconds for improved workability in tight spaces. Solid steel construction designed for maximum strength with minimal wall thickness made possible by tough materials, advanced processing technology, and optimal heat treatement.. Compact external diameter is among smallest in the world and ideal for tight spaces. Contains NM1-0810H, NM1-1012H, NM1-1214H, NM1-1417H, NM1-1719H, NM1-2224H NTM106H