Galvanized Steel Reducing Washer 1-1/2″ to 1/2″
https://dev.nsiindustries.com/product/galvanized-steel-reducing-washer-1-1-2-to-1-2/
The Bridgeport 1-1/2″ to 1/2″ Galvanized Steel Reducing Washer is used in pairs to reduce the size of knockout holes in a box or enclosure. The washer features raised flanges that allow for positive seating in the knockout.