Hello Mary, you use these to make your own sling. This is the wish bone you use at the end of the tube. Also here is the web link: http://www.scuba.com/scuba-gear-251/041171/Mares-Pneumatic-Speargun-Air-Pump.html
. If you have any other questions or would like to place an order please feel free to give us a call at 1.800.347.2822.