The 5/8 -18RH Female fitting to 1/4 BSP Female adapter lets you adapt your HTP gas connection from 1/4BSP to the more commonly found 5/8 -18RH gas fitting.
I've been happy with my HTP Welders and products. Peter Zilla has helped me out a ton.
5/8-18 RH Female to 1/4 BSP Female Adapter
This works just right to connect my 26 series torch to my HTP tig machine