ORIGINAL: CowboyLifesaver
It's best to buy the ones the have at your local shop for now. There are others that will work, but get a box of the right ones first and go from there. Never re-use them.
Oh and use 10 of them.
Good advice, I used to use 10-12 of them. If I did not the wings had a tendency to come up while flying. I almost crashed it one day because the wings came up in flight. Since then I modified them to bolt on wings and she is a fantastic bird now. Getting rid of the rubber bands was the best move I ever did with my Alpha 40.