This is a simple tactical sleeve to protect your ATU-100 tuner while in the field. Installs easily by sliding the tuner into the housing. For a semi-permanent install, add a dab of glue to the rear support section which will hold the case on, but make it easy to remove if needed.
The link for the tuner I purchased is:
https://a.co/d/3RMg1X2
The author marked this model as their own original creation.