Product review (5 stars): It's a mullion
This mullion works on a LMX28988 refrigerator model, from 2011, I believe.  I mention it because LG customer service could not confirm that this part ending in 103 would work--I think they specified a slightly different part number.  Has been in use for three months with no problems.  It was far more convenient to order this from amazon instead of the supplier that LG recommended.