I keep reading about the Beall collet kit. I looked them up on the internet and don't understand what they do that would make them better than a chuck or the MT mandrel with the adjustable rod.
Some prefer them for holding mandrels and report that problems they had with out of round turnings greatly improved.
I use mine for numerous things but don't have the need to use it to hold mandrels.
It is great for drilling blanks with a pattern in them.
It is great for drilling antler in conjunction with a Jacobs chuck.
I use it to hold the mini mandrel for making custom finials.
It is not a "must have" until you need it then it is indispensable.
Tangboy has the best prices I have seen.
I don't know why the Beall works so much better either, I just know it does. After I got mine, I put my adjustable "professional" mandrel in a workbench drawer and it hasn't come since. I wouldn't be without my Beall.