Shields
Shields work similarly to ERA.
Unlike ERA, however, shields have a slightly higher damage absorb value and a much larger HP pool. This allows them to survive a high number of lower-damage projectiles, such as autocannon and canister rounds, until their HP is fully depleted.
Against higher-caliber guns, if a shield has an absorb value of 40 damage per hit and 200 HP, an incoming 500 damage shell would first lose 40 damage to the absorb effect, then a further 200 damage to the shield's HP pool, leaving 260 damage to pass through to the target. The shield would then be destroyed once its HP had been depleted.
By comparison, autocannons are designed around continuous sustained fire and therefore deal relatively low damage per shot. Using the same values above, a 60 damage autocannon round striking the shield would have 40 damage absorbed, leaving only 20 damage applied to the shield's HP. This means it would take many hits to destroy the shield.
As a result, shields are especially effective against rapid-fire, low-damage weapons. Autocannons and canister rounds, which are normally very effective against ERA, can struggle significantly against shields because each hit removes only a small amount of shield HP.
If you'd like a deeper dive into ERA mechanics and how they interact with different shell types, let us know in the comments and we'll prepare extensive coverage on the topic.