From Hodgdon' web site:

"Our exclusive line of extruded rifle powders – Hodgdon Extreme – was developed to give shooters consistent performance, load after load, in even the most extreme heat and cold."

For a list powders that are part of the Extreme line, see:
http://www.hodgdon.com/smokeless/extreme/page4.php

Be sure to take the "Extreme Tour" at:
http://www.hodgdon.com/smokeless/extreme/index.php
Interesting info. (It consists of several web pages so be sure to look for the Continue/Forward buttons on each page.)

-Bob F.