• Heavy Duty Split Ring: High quality type 316 stainless steel. Corrosion-resistant, great for use in marine environments.
• Glossy and Shiny: Silver color, general and simple, can match with items of various colors.
• Two sizes included. Size Flat 25mm - Outer Diameter: 25mm, inner diameter: ~20.5mm. Thickness: ~2.4mm. Weight: ~2.8g/piece. Size 20mm - Outer Diameter: 20mm, inner diameter: ~16.4mm. Thickness: ~2.4mm. Weight: ~1.4 g/piece.
• Replace worn key ring keys links connectors. Package includes 5 pieces of 25mm 316 stainless steel flat split rings and 5 pieces of 20mm 316 stainless steel split rings.
• Suitable for organizing your house keys, office key, car key, motorcycle key, boat key, scuba diving, hanging cards, dog/pet leash, jewelry making, arts & crafts projects, etc. Available in 6 sizes: 20mm, 25mm, 30mm, Flat 30mm, Flat 25mm(inner diameter 20.5mm), Flat 25mm(inner diameter 21mm). (https://www.ebay.com/itm/264444870781)

Type 316 stainless steel contains 2-3% molybdenum which increases corrosion resistance, improves resistance to pitting in chloride ion solutions and increases strength at high temperatures.
Type 316 grade stainless steel is particularly effective in acidic environments. It is effective in protecting against corrosion caused by sulfuric, hydrochloric, acetic, formic, and tartaric acids, as well as acid sulfates and alkaline chlorides.
Great for use in marine environments.
Includes 2 sizes (https://www.ebay.com/itm/264444870781): 

(1) Outer Diameter: 25mm, inner diameter: ~20.5mm. Thickness: ~2.4mm. Weight: ~2.8g/piece.
(2) Outer Diameter: 20mm, inner diameter: ~16.4mm. Thickness: ~2.4mm. Weight: ~1.4 g/piece.
A perfect solution for attaching gears onto your BCD. 
Package includes: 
5x Flat 25mm 316 Stainless Steel Flat Key Ring Split Ring (inner diameter 19mm)
5x 20mm 316 Stainless Steel Key Ring Split Ring