Perks have been a Call of Duty series staple for 15 years, and while this system returns in the latest entry, it works much differently than before. In Call of Duty: Modern Warfare II, players gain access to four Perks — which is typically more than many entries have offered — but you have to earn two of them over the course of a match.

Because of the way Perks function in Modern Warfare II, even veteran players might struggle to optimize their setups. In this guide, we’ll explain how Perks work and which ones you should use in Modern Warfare II.

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Perks work differently in this game than in previous installments, as you can have up to four rather than only three. However, you start a match with only two from the Base tier, and must earn the others — from the Bonus and Ultimate tiers — over time. Gaining points speeds up the process of earning the additional two Perks, so you’ll want to play the objective as much as possible for maximum efficiency.

Reduce strength of enemy flash, stun, gas, shock, and EMP effects. Immune to Snapshot grenades.

Since it seems like so many players run flashes and stuns, having Battle Hardened can make or break certain situations. It’s also a great Perk because it makes you immune to Snapshots, which is also a popular piece of equipment.

Take reduced damage from non-killstreak explosives and fire.

Speaking of equipment, Bomb Squad is a highly useful Perk, allowing you to take reduced damage from explosives and fire. Many players like to run with Drill Charges and other explosives, so you’ll likely survive in many circumstances while using Bomb Squad. It’s a passive Perk that doesn’t really require you to do anything to make use of it.

Reload, use equipment, and swap weapons faster.

Another Perk that is all-around useful is Fast Hands, allowing you to reload, use equipment, and swap weapons faster. Considering the game’s animations are so slow compared to the time to kill (TTK), this Perk is highly effective, allowing you to re-challenge someone quickly in between reloads.

Eliminating players immediately triggers health regeneration. Capturing and holding objectives increases health regeneration rate.

Quick Fix is one of the most effective and consistent Perks in the game. It works just like its Warzone counterpart, triggering immediate health regeneration after securing an elimination. Considering enemies often challenge you back-to-back, having Quick Fix will allow you to take on your opponents more effectively, especially when they swarm you.