These are Keenserts -- I have been using these for high strength repairs for the last two decades. I believe that they were originally developed by Fairchild. Then the technology was picked up by ALCOA and marketed as "Tridair-Keenserts". For repairing heads, these are a stronger alternative to traditional Heli-Coil fasteners.
Here is a good "How-To" PDF, that explains the install and the benefits --
http://www.mediafire.com/?sharekey=77da8fd4484b5e25312dbd5f2bdc5062ec150950fe7248a45621d66e282a0ee8
(http://i357.photobucket.com/albums/oo18/goodfellow_2004/misc/PICT0373Medium.jpg)
(http://i357.photobucket.com/albums/oo18/goodfellow_2004/misc/PICT0374Medium.jpg)
(http://i357.photobucket.com/albums/oo18/goodfellow_2004/misc/PICT0376Medium.jpg)