Product review (5 stars): This is the solution LG did not tell you about for your mullion flap.
This is the solution for my lazy mullion flap issue. The refrigerator i used this on is a LG 25973ST- a consumers reports "favorite"  Unfortunately from the factory the flap spring was weak and caused it not fully retract or extend as needed. Frustrated for several months, I called LG support and they only for me to call my local parts agency at my expense and obtain parts ant MY expense!- That was not very satisfactory solution for me. I went to the local home improvement store and tried some of LG's latest refrigerators and noticed they had no problem with the flap closing fully- So searching the internet to see what others experienced, discovered this spring which is of a thicker gauge and I put it in in 10 minutes and IT SOLVED THE ISSUE. Thanks Amazon for helping me get this nagging issue fixed!