Here's a pic of them installed that I found (not mine). You can see the round velcro anchor in the floor. It is locked in place using the twist-loc or "T"
mechanism for our e53. The other side is a peel/stick adhesive with the "fuzzy" velcro attached to the mat. Works fine and is slightly easier to attach or detach vs the hook system.

Attached Images

 

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2005 X5 4.4 (Sterling on Truffle) w/sport everything
2011 Audi S4 (Prestige, DSG)
2012 Audi Q7 (Sport, S-Line)