A Perfect Ruby provides Fire Resist +40% when inserted in shields or off-hands, +38 to Life in body armor and headgear, and +15 to Minimum Fire Damage, +20 to Maximum Fire Damage in weapons.
A Perfect Ruby requires level 18 to use. When you socket an item with a Perfect Ruby, you increase the level requirement to level 18, unless it was already higher.
Horadric Cube recipes with Perfect Ruby
Crafting recipes with Perfect Ruby
A Perfect Ruby does not drop from any monsters or objects. It can drop from the Hellforge when destroying Mephisto's Soulstone, or from a gem shrine when holding a Flawless Ruby.