Quicksilver Reflex Booster (DXHR)

Quicksilver Reflex Booster is one of many augmentations available in Deus Ex: Human Revolution.

In-Game
The Quicksilver Reflex Booster, unlike a Takedown, allows for Double Takedowns, Lethal or Non-Lethal, though it may attract attention if it's used in the Lethal way as it is louder than a Stun.

For a Double Takedown to take effect you'll need two Enemies (or Civilians, Security, Police, etc.) close enough together to enable use of the Double Takedown. If you have "Show Cover/Takedown Prompts" Enabled, it will tell when you can do so by showing a symbol on the bottom of the screen, one of you Punching two people and one of you Stabbing two people, obviously one means Stun and the other means kill.

This is useful if faced with two enemies and you have no other options. This augment can save ammo, and it's a two-for-one takedown: two kills/stuns for one energy bar.

Note however that the system will always take the two closest visible targets, which can be a nuisance if civilians get targeted by mistake, leaving one of the intended "hostile" targets unharmed.