I'm not sure, but from what I've been told, the manufacturers were no longer allowed to make magnetics as of some date in '09, but they could continue to sell what was made until they run-out. They now have replacement electronic ballasts for F40 lamps for those who are dragging their feet, but it is just delaying the inevitable! Pretty soon, T12s will be history. My supplier still has some magnetics, in the oddball sizes that have been collecting dust for years! (circuline especially) The PITA is when you modernize a couple of fixtures in a building that has many fixtures! I always print a label reading "converted to electronic ballast, use only 32w T8 lamps" or something similar and stick it in an obvious location. Then I tell the maintenance guy to replace lamps with the EXACT lamps he takes out. Eventually, they will all need to be changed!