This ring has 3 charges, and it regains 1d3 expended charges daily at dawn. When you fail a Dexterity saving throw while wearing it, you can use your reaction to expend 1 of its charges to succeed on that saving throw instead.
RollQuest ships the D&D 2014 SRD as a content pack, on a 5e character sheet that does the maths - roll from the sheet and let the numbers work themselves out. Free to start.