Size: 15mm, 20mm, 25mm, 30mm, 38mm, 45mm, 50mm. 38mm D-ring Thickness: 3mm. 30mm D-ring Thickness: 3mm. 20mm D-ring Thickness: 2mm. 50mm D-ring Thickness: 3mm. Ideal for bag making, leathercraft, and custom accessories, they add structure, reliability, and a clean, contemporary finish to every project.