I can't figure this one out. I have a 36" Exmark Metro. I have ordered different blades in the past and some are different then others. The stock part # 103-6584. Now there are a lot of blades for sale that say they will replace that #. I was out in the garage yesterday comparing some old high lift blades I bought for this mower a year or two ago. They were the exact same overall length when set on top of one another. However, I did notice that the cutting edges themselves on one set was a good 1.5-2.0 inches longer/shorter. Why would that be? I just ordered some new ones with the part # 103-6584. When I got my confirmation e mail the company is sending me a blades with the part # 355-044 that replaces Exmark 103-6584. I have also noticed that depending on which replacement for Exmark 103-6584 you click on, because several come back, the blade length for a 36" mower can be 18" per blade or 17 15/16 per blade, why is that? Does anybody know?