Snap Fasteners - 21mm Sew-On in Black by Prym 341 172

These round sew-on snap fasteners are made from rust-proof brass. The sew-on snap fasteners consist of a spring section and a stud. The lower section (stud) is folded back - this protects the fabric from being damaged by sharp edges. The closure is easy to manipulate and just as easy to sew on; the four slots guarantee that the snap fasteners can be sewed on evenly.