The Gruber Stabilizer is the final unlock before the Zeller-H Advanced Sniper Rifle. This unlock must be equipped on the class customization sheet and will take up one slot. This stabilizer will negate nearly all of the sway induced by your breathing for a short time - enough for you to squeeze off a perfectly-aimed shot. Simply hit the "shift" key when you are ready to fire and the stabilizer will kick in, locking in your aim.
Finally, the Zeller-H Advanced Sniper Rifle is your last unlock up the chain in the Sniper career path. It is a heavy caliber rifle, able to mortally wound even the most heavily-armored infantryman with a body shot - and of course, instantly kill with a headshot. It is not, however, an anti-vehicle weapon. Shots fired at armored cockpits will only alert pilots to your presence with its loud report and heavy recoil.