Optical Sights - Available to all classes except HGs. Also commonly referred to as Telescopic Sights, these increase Critical Hit Chance and are vital for DPS dolls such as ARs and RFs with self-buffing skills.
Holographic Sight - Available to all except HGs. Holo Sights increase damage and accuracy but reduce rate of fire. This makes them more valuable on T-Dolls with damage dealing skills such as AR and SMGs with damaging grenades.
Red Dot Sight - Available to all classes except HGs. Red Dot Sights increase accuracy but reduce rate of fire. The need for increased accuracy is most common on MGs and SGs, although some DPS SMGs such as SMG SR-3MPSR-3MPSR-3MP also benefit greatly from the accuracy increase. It is worth noting that some enemies have no evasion stat so increasing accuracy against these targets does nothing. For information on which enemies have no evasion, check out the Enemy Index.
Suppressor - Available to all classes except MGs and SGs. Suppressors increase Critical Hit Chance, but by less than Optical Sights, and also increase Evasion. As HGs can only equip either these or Night Battle Equipment Suppressors are used by HGs and Evasion based SMGs to increase their survivability.
Night Battle Equipment - Available to all classes except RFs and MGs. These item reduces the Night Battle accuracy penalty by the percentage stated, multiplicatively. For example; a 90% PEQ will reduce the 90% night battle penalty by 81% (90% of the 90% penalty). PEQs reduce the penalty by a large amount for the doll equipping it and should be equipped by any damage dealing doll able to when fighting at night. Tactical Lights, or just Taclights, reduce the penalty by a small amount for the entire echelon in addition to a slight increase in Evasion. Taclights are best equipped by buffers and tanks supporting RFs and MGs at night, as the accuracy increase is substantial for these classes that cannot equip PEQs. Taclights may also provide a notable increase in survivability to SGs by increasing their very low base Evasion.
RMR Red Dot Sight - Available to HGs and MGs only. RMRs increase Critical Hit Chance, but by less than Optical Sights, and also accuracy, but less than Red Dots. These are useful for damage dealing HGs and MGs when going against enemies with evasion.
Choke - Exclusive to SGs. These increase accuracy and Clip Size, useful if you want your SGs to shoot longer and is a good alternative to optics in some cases.
High Velocity Ammo - Exclusive to ARs. This increases damage and should be used on all ARs not just because there is no alternative but because it is very good.
Hollow Point Ammo / Signal FLare - Available only to SMGs and HGs. Hollow Point increases firepower but reduces armor penetration. Signal Flares increases echelon accuracy while decreasing a minor amount of rate of fire. Flares should be the go-to option for buffers and tanks as their job is not to deal damage. Use hollow point ammo on damage dealing HGs and SMGs.
Armor Piercing Ammo - Available only to RFs and MGs, with a few exceptions being able to equip these from other classes. This ammo type increases armor penetration. A variant increases armor penetration by a smaller amount but also increases damage. This ammo type is absolutely necessary for dealing with the armored targets that you will encounter in battles.
Shotgun Flashbang - Exclusive to SGs. Flashbangs increase accuracy and nullifies damage up to 3 points post armor calculation taken from enemies hit by this shell. This is the most recommended shell type for SG main tanks.
Buckshot Ammo - Exclusive to SGs. Buckshots increase both damage and critical damage, with no drawbacks. This is the go-to ammo for most off-tank SGs.
Slug Ammo - Exclusive to SGs. Slugs increase accuracy and offers a significant increase in damage but reduces target count from 3 to 1. You should only expect to need slugs in rare situations where you need a SG but only expect to face a single target.
Birdshot Ammo - Exclusive to SGs. Birdshots increase rate of fire and target count to 5 but decreases critical damage. This is useful for t-dolls such as SG FO-12FO-12FO-12 and others to increase number of enemies knocked back.
SLAP Round - Exclusive to MGs. SLAP significantly increases armor penetration at the cost of an insignificant (for MGs) amount of rate of fire. Recommended only for enemies with a large armor value, however if you're lazy to swap between regular AP and SLAP, use SLAP.
Exoskeleton - Available only to ARs, SMGs, HGs. Comes in two different types, X and T. Exoskeletons increase evasion. X Series provide a moderate amount of evasion with no drawbacks, T Series provide a large amount of evasion and decreases damage. Only T Series are recommended as SMGs and HGs are expected to tank not deal damage. X Series does not suit AR class as you're better off using chips on ARs. You might use X Series on damage dealing SMGs and HGs as there is no damage reduction.
Ammunition Box - Exclusive to MGs. This increases MGs' Clip Size, increasing the number of shots that can be fired before the MG must reload, but decreases evasion. (doesn't matter that much as who would use MGs to tank?)
Camouflage Cape - Exclusive to RFs. Increases critical damage at the cost of lower movement speed. This makes it awkward to use in fights where you want to move your T-Dolls around to avoid damage and also lowers the entire echelon's advancement speed. To put this into perspective, base RF movement speed is 7, cloaks reduce this to 4.
Armor Plate - Exclusive to SGs. Armor Plates increase a T-Doll's armor value, reducing damage taken (assuming the enemy doesn't have enough armor penetration to ignore it), this allows SGs to tank significant amounts of damage from gunfire thanks to their high HP and the mitigation of their armor.
Chip - Available to ARs and SMGs only. Chips increase damage and changes rate of fire and critical damage depending on Focus Chip or Processor. ARs should default to using this on their t-doll slot, and potentially some damage-dealing SMGs and HGs are recommended to use these.
Rangefinder - Available only to a few RFs. These increases damage and reduces initial cooldown, by up to 80% with a maxed-out 5-star rangefinder, making it potentially useful for charged-shot RFs that deals damage through skill. Noted that there are charged shots that can deal critical damage, making choosing between Capes and Rangefinders something to consider. Some examples are RF TAC-50TAC-50TAC-50 and RF Kar98kKar98kKar98k.
Bipod - Exclusive to MGs. These increase accuracy and decrease reload speed but decrease movement speed. Potentially useful for second volley MGs such as MG NegevNegevNegev but your doll's move speed and echelon's advancement speed will be slowed to a turtle crawl.
Dolls that are being listed below don't follow general rule as they can be fitted with specific equipment that normally can't by Dolls their class or have different slot configuration.
Certain Dolls with exclusive equipments will receive bonus passive effects from equipping two or three of these equipments at once. For most units, the Costume Set is only available after Neural Upgrade. These effects and their requirements can be seen from the Index, either by accessing the Doll's index page, or by checking the appropriate search option from the equipment index.
Costume Sets were introduced for the collab units of Bounty Feast, but were only added to other units with client update 3.0200 and Gray Zone Exploration.