This is a long rainbow stocking cap. The small size will fit a teen to medium adult, large will fit a large adult. The finished sizes are:

Small: 19 inches around, 30 1/2 inches long
Large: 20 1/2 inches around, 32 inches long

The size difference is achieved by changing hook size for a finished gauge of:

Small: 11 Rows X 13 Stitches = 4 inches
Large: 10 rows X 12 Stitches = 4 inches

You will need less than one skein of each color Black, Red, Orange, Yellow, Green, Blue, and Purple, the hook required to reach your target gauge, and a pom pom maker.