This is a screw on Lectrosonics MM adaptor for the blank Lav Bullet (not included). The Lav Bullet is an aerodynamic stainless steel weight that can be attached to the connector end of a lavalier, and dropped innocently through clothing using the force of gravity. The Lav Bullet is simple, compact, and easy to use. The blank version is threaded for use with screw on adaptors.
Adaptor connection types vary: TA/mini XLR, 3 pin lemo, stereo mini, and Lectrosonics MM connectors.
The Lav Bullet Adaptors also work with the Lav Rod. How handy is that?