Alternate Helmets are different versions of the Warframes' original helmets. They have different designs on aesthetics, such as the addition of jiggle-bones (dubbed by Digital Extremes as "Dangly Bits") which was introduced in the second helmet series.
These helmets are considered as cosmetic items, as such they cannot replace original helmets in the Warframe's crafting process as a component. Prime Warframes use the same alternative helmets as their normal counterparts.
Helmets can be bought for 75 in the 'Equipment' section of the Market. Additionally, their blueprints can be acquired via completing Alerts missions.
Alternate helmets can be equipped in Arsenal using the "Appearance" tab when modifying a Warframe. They can be unequipped by reapplying the default skin.
At first release, each alternate helmet had stat modifications attached to them, which boosts one of the warframe's attributes while penalizing another. With the introduction of Nekros in Update 10, upcoming alternate helmets do not affect the stats of warframes.
As of Update 13.2.3, all helmets with stat modifications are replaced with stat-less version of the helmets in the Market and Alert missions. Helmets with stat modifications, now known with the prefix Arcane, can only be obtainable through the Trade System. Note that only completed helmets can be traded, and not blueprints. Players can also buy conversion blueprints to convert completed Arcane helmets to stat-less ones. Also note that Arcane helmets were removed from Warframe before an Xbox One release, so getting Arcane helmets in the Xbox One version is impossible.
The stat-less version of the helmets can also be acquired by purchasing a blueprint from the market for 1000, which converts the Arcane version of the helmet to its statless counterpart with no further cost.
Most stat decreases take place after the effects of Mods and Auras have been calculated; however, increases are calculated independently from alternate helmets. As such, stat increases are always directly dependent on base amounts, and are always the same amount regardless of Mods or Auras.
For example, Arcane Aurora Frost Helmet reduces Frost's maximum health by 5% and increases their armor by 25%. Without any Vitality, a rank 30 Frost's health becomes 300 − (300 × 0.05) = 285. With a maximum rank Vitality (+440% health), their base health becomes 300 + (100 × 4.4) = 740, and their total health after Aurora's effect becomes 740 − (740 × 0.05) = 703. However, because stat increases are independent, it will always provide exactly 190 + (190 × 0.25) = 237.5 armor whether or not the Frost has Steel Fiber equipped.