A different sort of "health pack" that lets you survive more hits. Basically, instead of regenerating your health, it gives you a shield that can wear off as more projectiles hit it. Basically, the shield takes your damage instead of your health, so you can survive for longer. Once the shield is zero, it takes health directly from you. At 100% shield, the shield gives you an extra 100% health, so you basically have "200%" health, which is equivelant to the equipment, mutation. Also, Pickup Booster adds on to a small shield [large shields are automatically 100% shield] and small shields are 25% Shield, so it becomes 65% shield with Pickup Booster.
In Raze 1, even if the shield is on full and is taking most of the damage, you will still get damaged, around one-tenth of the damage taken by the shield, so even if you're on 1% health with 100% shield, you will still get killed in 1 shot from the Magnum T-2. This shield is considered to be inferior to Raze 2's shield.