Not all meter covers are created equal.

TESCO Optical Port Adapter Accessories:

Cat. 1041-AC for GE/Aclara meters
Cat. 1041-CN for Centron meters
Cat. 1041-LG for Landis+Gyr meters
Cat. 1041-HY for Honeywell meters

These adapters snap onto the meter cover to provide a metal interface attachment for various pickups and probes.