The LS-166/U is used with the older style military radio sets which have a U-79/U audio connector. This is a standard magnetic speaker at 8 ohms at 3 watts. The speaker inclosure includes a 8:600 Ohm transformer to match the radio to the speaker. It has a switch located on the side to switch it between vehicle use and manpack. The connecting cord is terminated with the older style U-77/U connector.

You often find these speakers with the newer U-229 connector. It was quite common to cut off the old connector and replace it with a new one. Fundamentally though this speaker was not used with the new gear using the U-229 from the factory.