Product review (5 stars): Don't attempt repair with mullion in refrigerator, and inspect mullion before buying spring or new mullion!
Did not need to use it.

My Samsung refrigerator's mullion stopped working. I went straight to YouTube and watched two repair videos:  One, mullion not removed, the other, the mullion was removed.  Remove the mullion; it is so simple there is not excuse not to.  There are a number of slots in the mullion where a small screw driver blade may be inserted and used to pry mullion open - open full length of mullion.  Here's where it got interesting...

The spring that was in the mullion worked fine - the plastic channel in the mullion, where the longer leg of the spring was inserted, had snapped-off.  No place to insert the spring!  I noted that, toward the top of the mullion, there was an identical fitting for the spring, but, no spring was installed - it was a redundant piece, but, it had the hole/fitting for the door divider spring.  So, I swapped them, putting the broken part where the good part was, and the good part where the spring went.  I then took the original spring (still in mullion) and inserted into the fitting...and it works perfect.

Now I have an extra $5 spring, which is definitely better than an extra $80 mullion.