These plastic eyes are designed for use in amigurumi and other suffed creatures. The post of the eye goes through the fabric, and locks into place by way of the plastic washer (sometimes this takes a bit of force!). They must be installed before you stuff and sew-up your creature!
These eyes are a safer option than sewn-on button eyes, but there is no guarantee that they cannot be pulled off with wear and tear (and baby or animal chewing!) If making a stuffie for a baby or dog, we recommend that you make the eyes out of felt, or embroidery stitches.