ORIGINAL: bruce88123

Go to a store that sells medical supplies to Doctors or hospitals. They will be able to show you "surgical tubing"
Inside/outside diameter is about the same as describing pipe like you use in your home. The pipe needs to be a certain size. The tubing is not solid but has a hollow core. The diameter of the inner hollow core is the "inside diameter". If the "wall thickness" is too thick the rubber will be too strong. It will not only pull the wings off but if the wing is firmly attached it will make the wing structure fail or can even break the fuselage in half. Trying to climb too steep can cause this too. Climbing too shallow will let the plane fly too fast which is also bad. [:@] More things to learn.