This is a rivet to be used when fastening by superimposing thick leather. You hit and attach it by Tubular Rivet Peening Tool. (Hit it directly on （Stainless Steel Anvil,Heavy Anvil.)
A round hole punch that fits the tubular rivet, is a Round Hole Punch #10 (3.0 mm)
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Photo in the center: state struck by Tubular Rivet Peening Tool.
It finishes being cracked in chrysanthemum shape.
Photo on the right: back side of hitting Tubular Rivet. It stays firm.