You mean the exhaust gasket? No, don't reuse them, buy new ones.
Thank you!It's recommended you replace them. However, you can re use them depending on the condition.
I pulled my OEM exhaust off and had bought replacement gaskets prior in anticipation of replacing them. The gaskets were in excellent condition so I didn't use the new ones. There is no exhaust leakage at operating temperature.
If you see any indentations, wear, change in thickness (compared to a new gasket), or contamination that can't be cleaned off, then replace them.