I found these cute test tubes at Sams Club with gum already in them. I made the cards to go with them.
I cut the card 3.5 inches by 8.5 inches. I scored at 3.5 inches, 4.25 inches and 5 inches. Fold the card in half (on 4.25 inch score line) and measure up an inch from each side then cut to score line to make the opening for the test tube. I think they turned out cute.