I don't really think their is a MKI it is just an Infusion which has had some small changes over the years new sail cuts, non jibing boards. The Infusion MKII has the latest sail cuts, new longer boards with carbon trailing edges, rudders have carbon trailing edges, thicker wall boom, no non skid on front decks, new rubber non skid, better build quality, plastic isolation washers between ss hardware and aluminum. Their may be others just can't remember now. Also you can get options carbon tiller (very nice), 10:1 main, adjustable trap, tapered main and spin halyard, quick release rotation arm, stamasters.