My F450 takes 20” wiper blades and I’ve bought them from Amazon before. For the last month, the 20A model has been regularly dropping to $9 a blade. Several times a day it goes from around $17 down to $9 then back again. I just keep it in my cart in the “saved for later” section. I also keep the 20B, 24A, &18B but the price just changed by a couple cents.
Take advantage if you need a great 20” wiper blade AMAZON