This is a short stub KF-40 to 1-1/2 inch MALE G BSPP. This thread size is primarily used in Europe and Great Britain. This adapter converts "G" BSPP thread to a KF 40 flange which is more commonly used in the universal world wide vacuum market.

BSPP = British Standard Pipe Parallel (straight thread) and is often noted G, for example, G(1-1/2).

Adapter KF-40 to 1-1/2 inch Male BSPP Thread (British Standard Pipe Parallel), Stainless Steel
Common Dimensions:
A = 2-3/16 inch (55mm)
B = 1-3/8 inch (48mm)
C = 1-1/8 inch (41mm)
D = 1-3/16 inch (30mm)