Constructed from Chrome-Vanadium Steel , with mirror chrome finish further. Set Include: 14mm,18mm; 5/8",3/4",13/16 6-point design keeps a tight grip and prevents rounding off corners. Interior rubber insert secures and protects the spark plug during operation. Laser-etched size marking for the easy identification. It comes with a sturdy and convenient storage case. Keep each piece in the proper position. Meets or exceeds ANSI performance standards.