Durable sludgepak

 is a consumable in the Fallout 4 add-on Far Harbor.

Characteristics
This sludgepak adds 150 rads, but uses one's current level of radiation to determine the increase in damage resistance for twelve minutes:
 * at more than 150 rads, damage resistance is boosted by 25,
 * at more than 300 rads, damage resistance is boosted by 50,
 * at more than 500 rads, damage resistance is boosted by 75,
 * at more than 800 rads, damage resistance is boosted by 100.

Locations

 * Durable sludgepaks can be crafted at any chemistry station.