Internal Unions
Valco Internal Unions
Internal unions have female threads and a fitting detail for zero volume fittings. The nuts have male (external) threads.
Choose the union with the bore that matches the ID of the tubing. If the IDs are different, choose the union with a bore which matches the smaller tube bore.
Standard material is 300 series stainless. Also available in Hastelloy C, gold-plated stainless, and titanium versions.