A pair of F-4 Phantom II-like wings that replaces the stock wings on 2015 Generations Firefly (Fireflight), in a meager attempt (since the real Phantom II has low wings and then we have to change the entire fuselage) to make it more G1-like, and further differentiate its mold from Slingshot.
To put them on you need to remove the original wings of the figure. The best way to do that is the cut along the root of the wing until the metal pin is exposed, and then pry the wing out.
For more information please see TFW thread: http://www.tfw2005.com/boards/radicons-customs/1033020-shapeways-combiner-wars-fireflight-slingshot-upgrade-act-2-a.html
Also check out the Slingshot head and shoulder upgrades!