Thule Rapid Aero Load Bars are constructed of high strength aluminum that will not rust and are anodized to resist corrosion.  Rapid Aero Load Bars are engineered to work specifically with Thule Rapid Foot Packs.  Thule Rapid Feet attach to the under side of the bar in a short slot.  The Thule Fit Guide lists specific bar length for each vehicle and selecting a different bar length is not recommend as the under bar slot adjustment area is limited.  Across the top of the bar is a T-Slot with a removable rubber cover.  The rubber can be trimmed to allow attachment of bike mounts using Thule Xadapt adapters, compatible products are listed below.  Because the Thule Rapid Foot does not wrap around the bar there is more mounting area for bike mounts.  Bike mounts look great attached to Rapid Aero Bars with a clean integrated appearance.  Most other Thule accessories mount around the Rapid Aero Bars without any special adapters.  There are Thule accessories that can not attach to the Rapid Aero Bars, those items are listed below.  Thule Rapid Aero Bars do not include bar end caps because they are supplied with the Rapid Aero Foot Packs.

These Thule Products Require Adapters
Thule 518 - Echelon requires Xadapt 9
Thule 517 - Peloton requires Xadapt 9
Thule 516 - Prologue requires Xadapt 9
Thule 594 - Side Arm requires Xadapt 9 - used for rear of tray only.
Thule 598 - Criterium requires Xadapt 8
Thule 599XTR - Big Mouth requires Xadapt 2

These Thule Products Do Not Fit Rapid Aero Bars
Thule 558P - Tandem Carrier
Thule 884 - Roll Model
Thule 579XT - Canoe Carrier
Thule 847 - Outrigger II
Thule 556BLK - Surfboard Pads
Thule 562 - Vertical Ski Carrier
Thule 502 - Load Stop