I won't go with Kia Parts Now again. Bad experience returning an item and no refund.
To follow up on this thread, I did replace my Rain-X blades with OE arms and the difference was dramatic. I won't use aftermarket blades again if I can possibly avoid it. The arms were very reasonably priced at the dealer, and obviously no shipping. List for the 18" is $28.05, and for the 26" is $36.69, but the dealer only charged me $15.59 and $21.09 respectively, which was a nice surprise.