This writer will never be down with Ryron and Rener Gracie's whack Jiu Jitsu video correspondence courses and belt-testing, but there's no doubt these two sons of UFC founder Rorian Gracie know grappling inside and out. So, their "Gracie Breakdown" youtube series are almost always must-see videos.
Their UFC 168 version is no exception, especially with the gnarly arm bar submission wins from Jim Miller and Ronda Rousey to work with. Check out Ryron and Rener give detailed, fascinating step-by-step explanation of how Miller transitioned from a choke to an arm bar and submitted Fabricio Camoes as well as Rousey's fight-ending arm bar of Miesha Tate. The Gracie brothers explain how Rousey made adjustments from her first failed arm bar attempts to ultimately secure the last one.
Enjoy the technique talk from these two black belts, then go find a school to train in and practice for yourself!