Zenport Finger Knife RK08-10PK Finger Knife, Size 08, Finger Knives, BAG OF 10

Zenport RK08-10PK Finger Knife, Size 08, Finger Knives can be worn on the finger for cutting tape, opening boxes. Used for cutting. Also an excellent and inexpensive harvesting tool. 

Available in a variety of sizes. 

(Note: some put these on their pointer finger or over a glove which would require a larger ring size than your ring finger)