These black PET boston round bottles come with smooth silver disc top caps. PET offers a good barrier to gas and moisture, as well as a good resistance to heat. Simply push down on the top of the cap to flip the opposite side open. These plastic bottles could be a great option for packaging products like lotions, shampoos, and body wash. The 2 and 4 oz kits have a 0.27" orifice, while the 8 and 16 oz kits have a 0.31" orifice.