The tamper-evident band (also known as the pilfer-proof ring -however considered a misnomer given that pilfering is still technically possible) is a plastic or metal ring that is often found attached below a screw cap in bottles, connected by thin bridges. They can be molded along with the cap or slit afterwards. When unscrewing the cap, the ring breaks: the ring can separate from the cap, and two separate pieces remain, the sealing piece and the leftover ring; or the broken ring can form a "pigtail" still attached to the cap. The ring therefore is a tamper warning: if the seal between the ring and the cap is broken, it is an indication that the cap has been opened.
While tamper-evident bands are not considered a challenge for recycling, it is important that the band stays attached to the cap in case of refillable bottles, because it is hard to remove the rings from intact bottles in an economical way.
In a 1997 study on the potential hazards from carbonated drink bottles for the public, 7 people out of 180 admitted that they remove the tamper-evident band from bottles with scissors or knives.