Female 1/2-20 inverted flare. Used with GM brake lines to master cylinders with 3/8-24 inverted flare outlets. There are two, new adapter fitting.
MOPAR to GM BRAKE LINE ADAPTERS (1 pc) 9/16-20 to 9/16-18
GM BRAKE LINE ADAPTERS (2 pc) 1/2-20 to 3/8-24 and 9/16-18 to 3/8-24
SS Brake Line Adapters 3/8-24 - 1/2-20 & 9/16-18 , GM style M/C , Inv w/unions
2PC Master Cylinder Brake Line Adapters 9/16-18 & 1/2-20 x 3/8-24
Empi 18-1102 Brass Brake Line Adapters, 1/8NPT To 10mm, Pair