Bridgeport RWH-1 Reinforced Wire Holder, 2-1/4, Box of 50
https://nsiindustries.com/product/bridgeport-rwh-1-reinforced-wire-holder-2-1-4-box-of-50/
The Bridgeport Service Entrance Mast Porcelain Reinforced Wire Holder secures incoming overhead service entrance wires. The holder comes with a 3/8″ lag screw and approximately a 1″ by 15/16″ wire opening.