A 4 ounce PET Bullet is great for body sprays and perfumes and its small capacity is perfect as a convenient travel size. Also known as a Cosmo, the possibilities are endless when you pair with a pump, fine mist sprayer or continuous thread closure. The polyethylene terephthalate (PET) resin offers excellent surface gloss, a wide range of product compatibility, a good moisture barrier, a good oxygen barrier, and a good solvent (fragrance) barrier. The possibilities are endless when you pair with a pump, fine mist sprayer or continuous thread closure.