The Gray Matter Kit from Lunatic Fringe Yarns!
 
Five evenly spaced gray yarns along with black and white create a 7 value gradient study.  Use alone for a great study of value, or to highlight a color or double the gray yarns with a color to tone the color down incrementally.  All of the kits come with instructions to make 4 napkins.
 
Difficulty level for this kit is Advanced Beginner (Two fish). All kits have instructions for 4-shaft looms.  The 3/2 size yarn comes with instructions for a Rigid Heddle Loom as well as 4-shaft looms.