Well depending on the tubing. The stuff you use for aquariums (greenish haze on the tube) is really strong and powerful and I made sling shots out of that. But the new tubing that they use on IVs, and oxygen masks will not expand or stretch. Also there used to be yellowish tubes that were used for field work or enema kits (dont ask how I know that). They were my choice of materials for slingshot.

Matt