The package contains 20 pcs. Sets and 20 pcs. Waterproof O rings, making the rivets durable in deep water when used with O ringsAluminum body with aluminum shank, all aluminum without plastic; Corrosion-resistant and good stress makes you comfortable and saving, a tool is required for installation (tool is not included)The hole size is 5mm, the rivet head is about 10mm, the black part is 2.5cm, the detail measurement looks like a 3 photo-handle, the back side spread out in 3 directions to keep the materials together and make strong enough for mounting accessories, such as Fishing Rod HolderThese kayak rivets widely used in shipbuilding, containers, aerospace, automobile, furniture and more; They are great for many applications on the kayak, such as handles, pad eyes, fishing rod holders, etc. Color: BlackMaterial: MetalSize: 5.9cmPackage Contents:20 x Sets20 x Waterproof O-RingsOnly the above package content, other products are not included. Note: The light and different displays may cause the color of the item in the picture to be slightly different from the real thing. The allowed measurement error is +/- 1-3cm.