Aeroquip series 2083 (Ref. SAE 140137) Nipple-External Pipe/External Pipe Adapter.  Also available in stainless steel as part number 259-2083.
Items
2083 Pipe Adapter

2083 Nipple-External Pipe/External Pipe

2083 Pipe Adapter

2083 Nipple-External Pipe/External Pipe

2083 Pipe Adapter

2083 Nipple-External Pipe/External Pipe

2083 Pipe Adapter

2083 Nipple-External Pipe/External Pipe

2083 Pipe Adapter

2083 Nipple-External Pipe/External Pipe
Thread P1 N/A 1/8-27 N/A 1/4-18 N/A 1/4-18 N/A 3/8-18 N/A 3/8-18
Thread P2 N/A 1/8-27 N/A 1/8-27 N/A 1/4-18 N/A 1/4-18 N/A 3/8-18