Colossal Knurl

The Colossal Knurl is a item in Risk of Rain that increases the player's health by 40, health regeneration by 1.2 hp per second, and armor by 6.

Tactics
The Knurl is a good item for anyone, being an across-the-board boost to the player's durability; most notable are the armor boosts, a rare effect outside of leveling.

Character Synergies
The Knurl, while useful for every class, is best for the melee classes. Its health, regen, and defense boosts help mitigate the damage they take.

Item Synergies
It synergizes with other healing items, such as the Mysterious Vial, to provide continuous, unconditional healing. The flat HP boost is nice, but outclassed relatively soon by the Infusion; nonetheless, every drop of HP helps.

Trivia

 * Stacking these to obtain Armor isn't recommended, due to the difficulty of obtaining them. Chart