How do you execute a strike package in MW3 multiplayer?

Question

When playing multiplayer in COD: MW3 on the PC you are able to select strike packages when creating a class. How do you execute them during multiplayer?

Answer 1

The "support" and "assault" strike packages will give you rewards depending on how you set up your loadout, and how well you're doing in the current match.

When you've earned a reward, you'll get a notification on your HUD, and pressing a key will activate it. This key is configurable, but by default I believe it is 4.

The "specialist" strike package grants additional perks as you get kills without dying, but this does not require any sort of activation.