It is made of BUNA-N 70 durometer rubber compound. Creates a tight seal for fluid or gas connections and handy kit for shop toolroom or toolbox. On hand when needed saves time and money. The plastic compartment box is easy to store. The Precision Brand® 300 Piece O Ring Asst contains: 20 each of 3/32″ x 7/32″ x 1/16″ #005, 1/8″ x 1/4″ x 1/16″ #006, 5/32″ x 9/32″ x 1/16″ #007, and 3/16″ x 5/16″ x 1/16″ #008; 15 each of 7/32″ x 11/32″ x 1/16″ #009, 1/4″ x 3/8″ x 1/16″ #010, 5/16″ x 7/16″ x 1/16″ #011, 3/8″ x 1/2″ x 1/16″ #012, 3/8″ x 9/16″ x 3/32″ #110, 7/16″ x 5/8″ x 3/32″ #111, 1/2″ x 11/16″ x 3/32″ #112, 9/16″ x 3/4″ x 3/32″ #113, and 1″ x 1-1/4″ x 1/8″ #214; 10 each of 5/8″ x 13/16″ x 3/32″ #114, 11/16″ x 7/8″ x 3/32″ #115, 3/4″ x 1″ x 1/8″ #210, 13/16″ x 1-1/16″ x 1/8″ #211, 7/8″ x 1-1/8″ x 1/8″ #212, and 15/16″ x 1-3/16″ x 1/8″ #213; 5 each of 1-1/16″ x 1-5/16″ x 1/8″ #215, 1-1/8″ x 1-3/8″ x 1/8″ #216, 1-1/4″ x 1-1/2″ x 1/8″ #218, 1-3/8″ x 1-5/8″ x 1/8″ #220, and 1-1/2″ x 1-3/4″ x 1/8″ #222.