These magnetic clasps have a hole of approximately 50mm x 2mm or 3mm

They can be used with: 1 pc 30mm flat leather + 1 pc 20mm flat leather / 2 pcs 20mm flat leather + 1 pc 10mm flat leather / 5 pcs 10mm flat leather / 2 pcs 10mm flat leather + 6 pcs 5mm flat leather / 10 pcs 5mm flat leather