In Deus Ex, eight different weapon modifications are available. Each one either improves a weapon's attribute or adds an extra feature to the weapon. Each weapon is limited to a maximum of five upgrades per attribute. Not every modification is compatible with each weapon - as showed here.
When clamped to the frame of most projectile weapons, a harmonic balancer dampens the vertical motion produced by firing a projectile, resulting in increased accuracy. Each upgrade improves the base accuracy by 10%.
“
Almost any weapon that has a significant amount of vibration can be modified with a balancer; I've even seen it work with the mini-crossbow and a prototype plasma gun.
A laser targeting dot eliminates any inaccuracy resulting from the inability to visually gauge a projectile's point of impact.
There is a well known bug(though based on the description this might be deliberate) which makes all weapons equipped with the laser 100% accurate. Hovewer, attaching the Scope modification to the same weapon, either before or after attaching the Laser, will remove the accuracy effects of the Laser.
By lubricating the firing path with synthetic synovial fluid, the drag on fired projectiles is reduced with a consequent increase in range. Each upgrade improves range by 10%.
“
Coating the primary valve system of a flamethrower or plasma gun in synovial lubricant and then over-pressuring the delivery system will also result in an increase in range. Little trick I learned during field testing.