Brand: AIM Sports
This is the same bung supplied with the AiM Open-Tip EGT Thermocouple (Part No. MC-214). It is designed to be welded to your exhaust pipe, and the male threads accept the female compression nut on your 3/16" diameter thermocouple.
The AiM EGT Thermocouple that we normally stock (Part No. MC-003) is held in place in the exhaust pipe by means of a weld-on 5mm nut and does not use this bung.
We also offer the Auto Meter 1/8 NPT Male Compression Fitting Kit for 3/16" Probes (Part No. AM5255). Consider using that kit if your installation already has a 1/8 NPT female thread.