Pay Attention -- we advise you wait until the newborns are at least 5 days old before putting the collar on and make sure to check your pet's collar to see whether it's too loose or too tight. Please check if it is pressed in place to ensure that the identification ring is well fixed. Our products are easy to clean, not easy to break, and can be used repeatedly for a long time. Application -- there’s a adjustable hook and loop design to suit each pet’s size. Put them on the neck of your newborn puppies, so you can identify them with the collar’s color which are very bright, making it easy for you to track your pet. Size -- each puppy collar is 23cm/9.5 inch long and 1cm/0.4 inch wide. The length is adjustable, so it will adjust easily as your puppies grow and stay on very well. Material -- these puppy ID collars are made of premium nylon and polyester, have velvet on both sides and very lightweight, which is very comfortable and soft to your pets. Package Includes -- you will receive 15 pcs puppy collars of assorted colors, sufficient enough to meet your needs.