In Call of Duty: Modern Warfare 3 for the PC, PS3, Wii, and Xbox 360, you unlock the different perk care packages in Survival Mode as you progress in levels.
Here are the perk care packages you can unlock in Survival Mode, and what level must reach to unlock them.
Quickdraw – $3000, unlocked by default
Steady Aim – $3000, unlocked at level 8
Stalker – $4000, unlocked at level 22
Extreme Conditioning – $4000, unlocked at level 36
Sleight of Hand – $5000, unlocked at level 50
