The most common source of confusion regarding gear is the difference between Gear items and Gear fragments.

This is a whole Gear item, used on its own where applicable, or in Crafting recipes.

This is a Gear Fragment. It's used to create a full Gear Item. Note the symbol on the center of the icon, indicating that it's a Fragment.

Rewards will always deliver correctly after a mission is completed, but take care to note if the item is a Gear Item or a Gear Fragment, as this can cause confusion.