3d279c4a_2014_Medicare_Supplement_Plans__Benefit
[What Plan L Covers] Plan L does not covers Part B Excess Charges [Benefit] 
Part B Excess Charges Under federal law, doctors who don’t accept “assignment” (take Medicare’s approved amount as payment in full) may charge up to 15% more than the approved amount. You might want to think about this benefit if your doctors don’t accept assignment. You may also want this benefit if you have to stay in the hospital and can’t control whether the doctors you see accept assignment.
Blue Cross Blue Shield of Illinois - 2014 Medicare Supplement Plans
Benefit