For our tracks, and most other "C" channel tracks including Thule, A.R.E , and others with a channel measurement of approximately 3mm x 20MM, as shown below, you will use with Landing Pad 1 along with SkyLine Towers.
You may also be interested in this article, What are the dimensions of your tracks? which provides more information on the tracks themselves.
Example of a "C" Channel Track
Landing Pad 1
SkyLine Tower
Complete List of Parts to add a Base Rack to a shell
SkyLine Towers
Landing Pad 1
Crossbars: To determine the proper bar length measure from the center to center of the tracks and add 2" to each side
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