Tonneau capable bed rackrails?

t slot truck bed rack   Dan t slot cutter

does anyone know the dimension of bed to cabin roof, so one could figure out which rack height would work best for there needs? I found this

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real casino slot Toyota Tacoma T-Slot Tonneau Covers (For Retrax and Roll'n'Lock Tonneau The side remains open for quick access to your truck bed  Adjustable Crossbar Truck Bed Rack Includes the lockings system to lock the truck rack to the truck bed The mount wide of the bed rack is adjustable,