If you are interested in making liners for Michelle's son or if you have sons of your own that you would like to keep warm, please make sure you keep to the guidelines of the fiber. For example, the pattern calls for Cascade 220(found at your local yarn store) or Patons Classic Wool (found at Joann's), however, if you cannot find either of these (can also be found online), and would like to use a different brand, please feel free to do so, but please make sure you give it a burn test. The strict requirement is for safety reasons only. If it has any other fiber in it besides wool or it could be an inferior fiber, it could melt in extreme circumstances and we don't want that, neither will the soldier.
Burn test: Using a lighter, burn the end of the yarn and if it ashes, then it is a good wool to use. If the yarn melts, then you'll know that they put another fiber in the content and it is not 100% wool, or the sheep got lucky with an inflatable, not so lucky, sheep.