LuckyPet's Rivet-On Dog and Cat ID Tags are a great way to make sure your pet has an ID attached to their collar at all times. Available in Mirror Finish Stainless Steel, Matte Finish Stainless Steel, or Solid Brass, these tags come in 3 sizes to fit all collars. Please note that the collar thickness must be 1/8 inch or less for the included rivets to work. These tags are easy to install - after making the holes in your pet's collar, lay the tag on the collar and feed one rivet through each hole, then click the rivet cap onto the rivet. Finally, and most importantly, use a hammer on the rivet head to crush the rivet down until it is snug against the tag and collar, holding it securely in place.