Well, my fitting is circular. So, vstech, it looks what you have is the perfect fit. What's your source?

However, the rectangular plug seems to fit snugly and securely into the circular hole. Think it's OK like that?

__________________
14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 154k miles
06 E320 CDI "Rutherford", Black on Tan, 172k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife