2 1/4 (57mm) diameter brass abandon plug. Thread size is pipe thread size.

Manuals & Documentation
Catalog Number 825A
Manufacturer Legrand-Wiremold
Brand Legrand-Wiremold
Country of Origin China
Made in USA No
RoHS URL http://www.ideadigitalcontent.com/files/11311/ROH_Legrand_ROHS_statement.pdf
UPC 786564264507
GTIN 00786564264507