Benoire,  The compatible rails you are referring to is part # RGTK7 or P8N8P. They will both work with the Cable Management arm you discussed (part # NN006). P8N8p is shown below as requested. [IMAGE] Let me know if this clarifies things for you.    
Hi I've got a second hand R410 that came with Dell sliding ready rails which is rack mounted in my 22u rack.  I've just bought a new CMA for it but I've found that while the outside rails have the ears to fix the CMA (and supporting bracket), the inner rails that the R410 attaches to doesn't have them meaning that the arm won't attach. Can someone confirm whether the ready rails for the R410 do have the ears for the inner rail and if so, does anyone have the part number? If anyone can take a photo of them if possible that would be grand. Cheers, Chris
Dell PowerEdge R410 Sliding Ready Rails - No CMA connector on inside rail