Some exhaust systems have the bung for the 02 sensors and the question comes up about what size and thread are they.

You can find plugs at NAPA stores, #35299 will work great to plug the bungs.

NAPA® Online (http://www.napaonline.com)

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Item#: EXH35299
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Price: $8.19
tax and shipping not included

Disclaimer: The stated price may vary from the in store price and may change at anytime.

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Attributes:
Product Features:Used for HEGO Connector when Oxygen Sensor Not Required.
Dimensions:M18 x 1" Zinc Plated Plug