Installing refurbed fuel injectors. There is a clip that secures the top of the fuel injector into the fuel rail and ensures no movement up and down. There are actually two ridges that the clip can secure into. If you look at photo, there is a ridge just below the rubber O-ring at the top. Then, there is another ridge that also has the green plastic clip. Which of these ridges do I clip into? I originally thought it was the lower one with the green ring and the plastic ring ensured that the clip was tightly secured as well. But, it is nearly impossible for me to get this thing clipped in - I just broke two and still have a couple more to go.

I am now thinking I am supposed to clip the clips into the top ring closer to the O-ring. If so, what is the green plastic ring for?

 

The clips go at the top. The slots on the sides of the clips line up and grab the flared ends of the fuel rail bells. That way the injectors can't move away from the fuel rail. They only go on one way, injector clip bits down in the upper slot.

Maybe the green is color coding from the manufacturer of refurber. The Mustang 4-hole injectors in my 94 have an orange band.