Marine grade 304 stainless steel - strength and rust resistance High precision polished for sleek appearance. Non-rusting stainless steel - versatile strap, binding and rigging hardware Perfect for marine, diving and outdoor harsh-condition applications; luggage & bags, saddles Rings are sized by thickness by inside diameter Size Chart: Thickness x Inner Diameter 7 x 40 mm/ 0.28 x 1.6 inch 7 x 50 mm/ 0.28 x 2 inch 8 x 60 mm/ 0.31 x 2.4 inch 8 x 70 mm/ 0.31 x 2.8 inch 8 x 80 mm/ 0.31 x 3.1 inch 10 x 60 mm/ 0.4 x 2.4 inch 10 x 70 mm/ 0.4 x 2.8 inch 10 x 80 mm/ 0.4 x 3.1 inch 10 x 90 mm/ 0.4 x 3.5 inch 10 x 100 mm/ 0.4 x 3.9 inch Package Includes: 1 Piece Stainless Steel O (4 Pack) Note: 0.1mm-2mm measurement error exists, especially from different batches.