BaseClips from Yakima are required for the complete system of a Yakima BaseLine roof rack. A clip set (set of 2) are required per set of BaseLine Towers. 

Have 2 BaseLine Towers, you'll need one set of BaseLine Clips. 

Have 4 BaseLine Towers, you'll need two sets of BaseLine Clips. 

These Clips are vehicle specific, so make sure you use the vehicle fit/tech manual to ensure the correct fitment. 

Included: Two metal clips with rubber contact patch, two rubber base pads, and measurement sheet.