I LOVE these pants for kids. They look like normal jeans or cords or slacks or what-have-you, and the length is the length that you'd expect for the size, but hidden inside the waistband is a length of buttonhole elastic, and on either side of the casing--a button!
No more Husky or Slim, no worries with hand-me-downs, no baggy waists for the kid who just had a growth spurt, and the kid who actually cares about such thing doesn't have to wear "baby" pants that are obviously elastic-waisted (I told her she could also call them old lady pants, but still...).
These pants can be tricky, though, because if that button works its way out of the elastic, or (more likely) that kid who cares about such things tries to adjust the elastic herself and leaves the elastic off of the button, AND it goes through the wash, then the elastic will get lost inside the waistband, rendering it useless.
Here's how to fix it:
Take hold of the other end of the buttonhole elastic and pull it all the way out of the waistband:
Pin a safety pin through the elastic, about 1/2" from one end:
--and then all the way through:
Now keep that elastic buttoned on BOTH ends this time, will you?