Package includes 20 pcs rivet kits and 20 pcs waterproof O-rings, designed to enhance durability in wet environments when used with the O-rings. Aluminum body with aluminum mandrel, all-metal constructionno plastic. Corrosion-resistant and reliable for strong performance. A rivet tool is required for installation (tool not included). Hole size is 5mm, rivet head diameter is approximately 10mm, black stem length is 2.5cm. Refer to the third image for detailed measurements. Grip rivet style features a back side that expands in three directions to securely hold materials, ideal for mounting accessories such as rod holders. These rivets are commonly used in marine, industrial, aviation, automotive, and furniture applications. Suitable for kayak accessories including handles, pad eyes, and rod holders. Color: black. Material: metal. Package dimensions: 5.9cm. Package contents: 20 x rivet kits, 20 x waterproof O-rings. The package includes only the items listed above; other products are not included. Note: Lighting and display differences may cause slight color variation between the image and the actual item. Measurement error allowance is +/- 1-3cm.