These things come and go. They have been around in the manufactured home community for over a decade. It is what they snap the modules together with. For a while AMP was selling these as the way to fix the 90c/<old>NM ceiling box problem.
After a lot of hubbub they removed the 336-21 (now 334.40) language from their ads. I think we went through this a year or so ago here and the language was gone, only the 551 reference. I see it is back.
[This message has been edited by gfretwell (edited 01-25-2006).]
