Dritz Double-Cap Rivets are used to secure multiple layers of a material together and as a decorative accent on handmade projects and accessories. The Double-Cap provides a finished appearance on the front and back side of your project. 8 mm cap x 6 mm post. Great to use as a no-sew options for projects where it is hard to reach into tight areas or hard to stitch through thick layers with a sewing machine. Suitable for fabric, vinyl, leather, canvas, belting and other materials.