Now Includes Bottle Caps! No need to clean off the leftover soda and sticky gunk under soda pop labels! Steve Spangler uses these high-quality plastic bottles for his in-service teachers' workshops and our teachers keep requesting them! Great for use as a tank for your Cartesian ...Now Includes Bottle Caps! No need to clean off the leftover soda and sticky gunk under soda pop labels! Steve Spangler uses these high-quality plastic bottles for his in-service teachers' workshops and our teachers keep requesting them! Great for use as a tank for your Cartesian divers, Tornado Tube inventions, or Soda Pop experiments! Great for use as a tank for your Cartesian divers Also used for Tornado Tube inventions, or Soda Pop experiments Sold in packs of 6 or 30Recommended for children ages 3 and up.