Silver plated Britannia pewter TierraCast® 9mm Celtic decorative washers for riveting. 3mm center holes are perfect for use with TierraCast rivets. Great for leather! Although these Celtic knot findings are designed as rivet accents, they are also excellent for small choker centerpieces, as well as links or connectors for a wide variety of Celtic jewelry designs. Silver plate is a thin surface layer of actual silver.