Rear Brake and Drum replacement parts

hi all

i'm looking at parts online for a rear brake kit for my gen 2 prius. i'm at 165k. i'm looking at two different kinds of kits at the typical online parts store. one has the kit with the wheel cylinders and one without. when would it be necessary to get the kit with the wheel cylinders vs without? i'm looking at a centric kit with the cylinders and a power stop kit without them. the wheel cylinders are the only difference.