Killstreak kit

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The loot you'll get from completing a Tour of Duty will work a bit differently for the Two Cities Tour. Completing a Two Cities Tour automatically grants you a Killstreak Kit, which you can apply to any weapon to transform it into a Killstreak weapon. Completing the Tour also grants you a fabricator and spare parts that you can use to craft progressively rarer Killstreak Kits, which will add cool visual effects to your weapon and eventually even your character. — Two Cities Update

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Killstreak Kits were officially announced on November 20, 2013. Completing a Two Cities Tour will automatically earn you a Killstreak Kit, which can transform any weapon to a Killstreak weapon. As the player completes more tours, they will build up a collection of fabricators. These items will allow them to craft even rarer killstreaks, granting special effects to the weapon they are applied to.