Seat springs come in a variety of heights. The height you need is dependent on the height of your seat frame, and the height and shape of the crown you are looking to achieve in your seat. Shorter springs can be used for a more flat surface, and longer springs for a more firm, round surface. Keep in mind though, a spring can be too tall and the pressure from tying it down can cause the spring twine to break prematurely. The springs should always rise above the frame a little though. Here I have made available 4" - 12" spring heights.