I believe they are a -6 (dash six) or 3/8th of an inch.
On most fitting there will be a "dash number" the "dash number" is based on 16th of an inch.
-2 = 2/16 or 1/8 inch
-4 = 4/16 or 1/4 inch
-6 = 6/16 or 3/8 inch
-8 = 8/16 or 1/2 inch
-10 = 10/16 or 5/8 inch
-12 = 12/16 or 3/4 inch
-14 = 14/16 or 7/8 inch
-16 = 16/16 or 1 inch
Look for the dash number.