We got them through the case ih dealer.. Cant remember the cost, less than 500 im thinking. I couldnt find any aftermarket or used ones. The directions reccomend using a 4" smaller blade on them. We went only 2". Probably change it out come spring. Its for the rear only. I put a 2" smaller blade on the outside of the front gangs and they still throw a pile of dirt! Ive been thinking about tapering the the outside 2 blades to 18", 20" and leave the rest at 22". The furrow fillers certainly help though!