Some need to be researched while others are applied directly following their purchase, respectively. Upgrades can be found either while on a mission or browsing the local kiosk at the marketplace. Additionally, players can no longer directly modify their weapons. Now, instead of having to worry about heat management, players can collect ammunition in the form of 'thermal clips.' Each clip has a certain amount of rounds that can be fired before it needs to be discharged. The upgrade and modification system for weapons changed quite a bit in Mass Effect 2.
