Centerpieces are most commonly used for holiday gatherings and special events where food will be served; a wedding for example. It is an all-around arrangement which is attractive from all sides and never more than 12 inches tall. Generally it should take the shape of the table; round for round or square and oblong for oval or rectangular and its size should be in scale with the table.
The size you should order will depend on the number of guests your table will seat: 2-4 Guests = Small, 4-6 Guests = Medium, 6-8 Guests = Large, 8-12 Guests = Deluxe or Premier, More than 12? You must have a very long table and could use multiple smaller sizes.