This is a double set of the same "Backpack Weapons" and extra backpack piece originally included with my "Titans Return Rumble/Frenzy Kit" item, made seperately and in a 2-pack at the request of TFW2005 user "cwgall". The extra backpack piece pegs into the robot mode back of Rumble/Frenzy via a custom peg, then the "backpack weapons" plug into the backpack piece via two 5mm peg holes. Due to the way the arms of the Rumble/Frenzy mold are designed, he cannot actually hold the "backpack weapons" as blasters, but other figures that feature 5mm peg hands could if you wanted to. Lastly, with the backpack piece plugged in, Rumble/Frenzy is not able to transform.
Original "Titans Return Rumble/Frenzy Kit" item:
https://www.shapeways.com/product/PJJ7N8VAV/titans-return-rumble-frenzy-kit