I've seen different companies and different books all list different measurements.

Finally called my local Mazda and got the OE measurements directly from them.

24" for driver's side; 18" for passenger

Thank you Mazda of Orange for the measurements, now going to Costco online to buy for $5.99

 

You don't list the year of your car. For the 2016+ CX-9, skip Costco. They don't have any that fit the wiper arm connector. There are a couple of choices. The rubber inserts from a dealership are easy to install (bit of a trick getting the first one started, after that, easy) and don't cost much. Trico Exact Fit and identical NAPA wipers do fit right on without adapters. While you got the length from your dealer (my measuring tape works as well), you did not the the connector type. I've seen a couple of names for it from different companies, so not even that is standardized. By the way, my Toyota Prius uses the same connector but different length blades.

Many of the wiper makers' listings show the 2015 size and connector under the listing for the 2016. Won't work.