RBF (Reinforced Buffer retainer, Forward Controls) is a strengthened AR buffer retainer machined with Swiss machines from 17-4 stainless steel bar stock, and heat treated to H900 hardness.  RBF features a reinforced tip that is 10% larger (0.102) than TDP spec (0.093).  We don't want RBF to be timed (as the case with a rectangular tip), so RBF retains the TDP buffer retainer's versatile round tip, and is installed per TM instructions.  10% is as much as we could increase before encountering receiver extension timing incompatibilities.

 

When all the systems in an AR function properly, one could argue that a reinforced buffer retainer isn't necessary.  We agree, except mix and match parts from different manufacturers and their varying adherence to TDP specs, tolerance stacking is far from the exception.  Many of us have had this inexpensive part break and toss its tip into the lower receiver, usually in the trigger group and cause a jam.  RBF's billet construction and reinforced tip aim to mitigate this, it could be viewed as cheap insurance, even if the way we make it is anything but cheap.