So, what I did was follow Rob's re-build video . . . . . only, instead of breaking off the bottom end of the unit, I tried to unscrew it. I've done a few, now, and have had better than 50% success in being able to recycle the old 510+ stem and tube nipple thingy (← official term). It is very easy to break, tho, and sometimes just won't come apart with less force than it takes to damage it. (Not designed for recycling). Also, I've overtightened at least one and must've cracked it, cause when I went to remove it the next time, it just fell out (must've been holding on by a thread . . . . literally). The amount of force it takes to install well vs. the amount of force it takes to break it . . . .. I wouldn't do one unless I had replacement parts in hand.