What is a CMBS B-Piece?

When CMBS loans are pooled together to create commercial mortgage backed securities, these securities vary in credit quality and payment priority. Typically, they are divided between investment grade securities, (AAA/Aaa through BBB-/Baa3) and sub-investment grade securities (BB+/Ba1 through B-/B3). While the A-class bondholders are paid first, B-piece bondholders must wait until all A-class bondholders are fully paid before they receive any compensation. Due to their higher risk, however, B-piece CMBS offer investors significantly higher returns when compared to A-rated CMBS.