So I sent my 24-105L in to Canon the other day. My Red ring broke off about a year or two ago. I had Canon on the phone for a different question the other day and decided to ask how much I could get a red ring for.
They told me the red ring on this specific lens is a shock absorber and keeps things from hitting where the front assembly separates. Apparently this is an important part of the front of this lens and not just decoration. The front of the lens needs to come off to get the ring back on so I figured let me send it to them and get an estimate.
I just got the estimate. $143 AFTER my 20% CPS discount!!!!
The part was $19 and the rest is labor to get the ring back on. A "cleaning and calibration" is included.