The 9670 has a double v belt, 9770 and 9870 have a triple upper belt. There is an hxe part number belt for the 9670 as well. Also if a person has time, check the alignment of both chopper belts, both my 9670s were misaligned from factory. That being said, I still blew one belt, after I re-aligned everything during my predelivery. I am currently keeping a spare upper chopper belt on hand, I had blown one last year as well, droppng straw! Also the new belt costs about $300 more than the original, so if possible try and get warranty.