2018 Subaru Crosstrek Limited w/Eyesight
It's a strut, not a shock. It goes on, comes off as one complete unit (spring, strut, & mount). Nobody makes a complete, ready to install OEM assembly like Monroe or even Honda. To replace the strut, you need to pull the assembly off the car, compress the spring, remove the nut, and swap the new strut in and reverse the procedure. It is a good idea to replace the strut mount while you have the strut disassembled. It's cheap insurance so you don't have to tear it out again.