It is very important to provide as much details as possible if you do not know what studs type  is , because one of the reasons is that some diameters  1/4' and 3/8” cross into both of the CD Weld Studs and Arc Weld stud realms. 

For examples :  3/8' diameter studs can Flanged CD Weld Stud or Headed Concrete Anchor .  Same diameter, but these two studs are very different from one another and used in  different purposes.

Provided below information  will help to  narrow it down:

1.Base material & thickness ;

2.Application: is it a full penetration weld or a surface attachment ;

3. Stud material & grade needed ;

4. the torque rating requirements ;

5. power requirements of the machine .