When shopping for popup sprinklers the three main things to consider in a popup are the shaft seal, the adjustment ratchet, and the retraction spring.
The shaft seal is located around the hole in the popup cap. The seal keeps water from leaking around the shaft as it rises to irrigate your gardens.
The popup shaft should have an adjustment ratchet. The ratchet mechanism slides along ribs in the body of the popup. The ratchet allows you to fine tune the sprinkler adjustment from left to right to help eliminate excessive overspray onto walks and other areas you don’t want to irrigate. A higher quality head will have an adjustment rachet that will not strip out after a couple of turns. If the rachet strips it will not hold the proper adjustment. A lower quality head may not have this mechanism as part of the head and the only way to adjust the head is to turn the whole body.
The retraction spring in a popup can vary in strength. A higher quality head will have a spring that holds its tension and pulls the popup back into the body years after it has been installed. I don’t recommend buying popups that have a soft spring.