These glass doll eyes are great for DIY projects. You can use them to decorate dolls or make unique jewelry. To use, just find a suitable spot on your project and attach the eyes as you like. Remember, since they're not self - adhesive, you may need some glue. When it comes to maintenance, keep them away from sharp objects to avoid scratches. Also, store them in a dry place. Regarding the size, note that there might be a 1 - 2mm error due to manual measurement. And don't be surprised if the colors look a bit different from the pictures because of chromatic aberration. Have fun with your DIY projects!