This item is one test tube with a lip on the open end.
The lipped tube fits into a 1/2 inch diameter hole and is designed as a bud vase insert tube. Essentially it is intended to improve the appearance of the hole edge (if you do woodwork like I do) or to add a nice contrasting color ring around the hole. The plastics may not be waterproof so I would stick to using fake or dried flowers in your vase.
Note that this store also offers test tubes sprued together. In general you might be better off purchasing several of this single tube model than the sprued version if you are purchasing the natural unprocessed white versatile plastic. However the sprued versions will likely be cheaper on a per part basis if you are purchasing the processed dyed plastic versions. (Although things can change when Shapeways updates their pricing formula.) Be sure to check the various options in the store to determine what's the better pricing option at the time of ordering.