Master Cyl Flare Nut Source
Rearward port, bubble flare, 11mm x 1.5 fitting, for tube size 3/16" OD
Forward port, bubble flare, 12mm x 1.0 fitting, for tube size 6mm OD
Both of the OEM fittings have a 13mm hex wrench size.
Both the 11mm x 1.5 (unusually coarse thread for brake line) and 12mm x 1.0 (unusually fine thread for a 12mm thread) thread sizes are not normally encountered in brake line work.
GM part numbers, for the 11 x 1.5 tube nut #11515872, for the 12 x 1.0 tube nut # 11516405
Forward port, bubble flare, 12mm x 1.0 fitting, for tube size 6mm OD
Both of the OEM fittings have a 13mm hex wrench size.
Both the 11mm x 1.5 (unusually coarse thread for brake line) and 12mm x 1.0 (unusually fine thread for a 12mm thread) thread sizes are not normally encountered in brake line work.
GM part numbers, for the 11 x 1.5 tube nut #11515872, for the 12 x 1.0 tube nut # 11516405
