The 9/16-18UNF Hoses have the Standard Scuba 2nd Stage Fitting on one end, and a 1/4"MPT on the other end.
The 3/8-24UNF Hoses have the Standard Scuba 1st Stage Fitting on one end, and a 1/4"MPT on the other end.
The 9/16-18UNF Hoses have the Standard Scuba 2nd Stage Fitting on one end, and a 1/4"MPT on the other end.
The 3/8-24UNF Hoses have the Standard Scuba 1st Stage Fitting on one end, and a 1/4"MPT on the other end.