Lock-A-Liner, 3/4″, Polypropylene for Insulated Connectors
https://hotfix.nsiindustries.com/product/lock-a-liner-3-4-polypropylene-for-insulated-connectors/
The Bridgeport 3/4-Inch Polypropylene Lock-A-Liner liner lock converts ordinary bushings and connectors to code-approved insulating bushings and connectors.