4 more metric taps and 4 more metric dies.
Both sets are made by Kastar. The only difference is the sizes included and the price. Kastar makes the exact same kits for Snap-on as well except they sell for forty bucks more than the Craftsman.
http://www.aeincorporated.com/Kastar/?page=store&category=7&page_num=2&num_items_to_display=10
http://buy1.snapon.com/catalog/item.asp?item_ID=56049&group_ID=1148
If you have full sets of tap & die sets, why would a guy need these?