Sorry I can't remember, I gave the machine to my son so it's not here for me to look at. The way I picked the size was by whatching the needle slide down a 346 thread at about 45 degrees. 346 is all I used to work with. That Boss is an excelent maching for sewing horsehide holsters. Jumping off point for bobbin tension is about 16 .oz of pull and then fine tune from there. Trigger pull scale is what I used to use to measure it.
After you get used to it you'll find the Boss to be a perfect holster machine.