Ferrea valve safeguards are manufactured from high quality 4140 steel and machined to exact tolerances. The security features are heat treated for maximum strength and black finished for an attractive appearance Fits: ALFA ROMEO GTA 156 V6 3.2L - DOHC 24 VALVE - 2002-2005 Reference: 7mm. Radial groove. Ferrea valve locks are manufactured from high quality 4140 steel and machined to exact tolerances. Protections are heat treated for maximum strength and finished in black for an attractive look. Fits: ALFA ROMEO GTA 156 V6 3.2L - DOHC 24 VALVE - 2002-2005 References: 7 mm. Radial groove.