Ring of Protection

Ring, Rare (Requires Attunement)

You gain a +1 bonus to

An Armor Class (AC) is the target number for an attack roll. AC represents how difficult it is to hit a target.

Your base AC calculation is 10 plus your Dexterity modifier. If a rule gives you another base AC calculation, you choose which calculation to use; you can't use more than one. See also Attack Roll.

and saving throws while wearing this ring.

Source: Dungeon Master's Guide, p. 294