Shrink bands are placed around the bottle neck and closure in the final step. Heat is then applied, and the shrink band melts to form a tight tamper-evident seal. Polyvinyl choride (PVC) is marked with the resin identification code of 3. Over half of PVC is cholorine, requiring less petroleum that other plastics. PVC has medium clarity, good chemical resistance, good impact resistance, medium rigidity, and medium scratch resistance.