This is a mount for a Quad Lock Gimbal Adaptor and any compatible Quad Lock 360 head (I'm using a MAG head since it's lighter - 27.5 grams vs 61.5 grams for the MAG wireless charging head). Note that the gimbal adapter doesn't come with a thumbscrew, so you'll need to print your own (search “m4 thumbscrew” on Printables - some require an M4 nut) or get some knurled M4 thumbscrews.
Tested so far on a few Delta flights and it fits great in the tray table slot. YMMV depending on the seat back configuration.
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The author marked this model as their own original creation.