These Bungs allow you to store additional elastic on a winder giving you the opportunity to set the elastic at differing tensions. It is made from a very light plastic that is very robust and help keeps weight to a minimum. The single bung pack comes with an extractor rod that allows you to remove the bung effortlessly. The second pack comes with two bungs and both can be cut down to fit most top sections. These bungs are idea for commecial type waters and perfect for use with the Hollo range of elastics.