The plastic can get brittle, and break during disassembly. This is a original part. It does fit various places on the vehicles in the list below. Price is for one nut.
Fits: Audi RS2, 80, B4, A4, A4 quattro, S4 and RS4 B5 / B6 / sedan and avant, Allroad / A6 / S6 / RS 6 C5, C6, A3 / S3 8L, 100 / 100 quattro / S4 / S6 / S6 Plus C4. 1991-2005. Referance for original Audi parts numbers: 4A0853379E - 4A0 853 379 E