100 pieces per bag. Used with socket, eyelet and stud to form industrial snaps. Used to fasten material together or snap fasten material to hard surface using screw stud . Commonly used to fasten down boat covers. The diameter on these is 5/8" across. To attach fabric to a boat use this part along with these Stainless Steel Stud or Nickel Plated Stud and a Socket. To attach 2 pieces of fabric use this along with these 3 parts: Socket, Eyelets and Studs.