The opening is 62mm X 73mm in diameter.
The ACT-0073 (previously MAG-J73C005) is a split-core current transformer with input rating of 500 - 1000 Amps. It outputs a corresponding 5A output. This split-core transformer is made with high quality nickel laminations. Split-core transformers are ideal for installation on existing electrical wiring by snapping around the conductor. The ACT-0073 has a self-locking mechanism.