One thing to remember, in some applications, the Bilstein shocks get installed “upside down”. Where the body is at the top and the rod is on the bottom. When a Bilstein is installed correctly, the logo will always be right side up. If the logo is upside down, then it’s installed wrong.
I know this because the first front ones I got for my Excursion, were the F-2/350 ones, not the Excursion ones (yes, even though the Excursion and trucks have the same suspension, Bilstein specs different shocks). The Excursion part number installs rod up, but the pickup part number installs rod down.
I mention this because in the picture on amazon, the top two would be installed rod down (blue bellows closer to the ground (yes they do come with the bellows, if pictured)), and the bottom two would be rod up. My guess is the top two are the front shocks and the bottom are the rears in this case.
For example, for my F-150, the rears come with bellows, and installs upside down (bellows towards ground, and the fronts install rod up, with no bellows. Just wish they were a little closer to the price for the IDIs....
Bilstein 24-187381 33-187396 B6 4600 Series Set of 4 Monotube Replacement Gas Charged Shock Absorbers for 10-12 Ford F-150 RWD
https://www.amazon.com/dp/B01MXZLJI9/ref=cm_sw_r_cp_tai_mqSADbYHM7JTS