Feature: 1. Perfect Fitmen: According to the original factory specifications, O rings reference OE number is 4138938. Wonderful replacement for Hitachi EX excavator. 2. Wide Application: Used in pipelines, machinery, hydraulic and pneumatic maintenance, faucets, garages, workshops, automobiles, doors and windows, electrical appliances, bearings, pumps, etc. 3. Premium Material: Hydrogenated Nitrile Butadiene Rubber (HNBR), also known as Highly Saturated Nitrile Butadiene Rubber (HSN), is a special class of Nitrile Butadiene Rubber (NBR) that can meet application temperatures between ‑45 degrees Celsius and 165 degrees Celsius. 4. High Oil Resistance: Resistant to heat, low/high temperatures, air, water, petroleum products, mineral and hydraulic oils, natural gas, kerosene, silicone oils, non aromatic fuels and solvents for long lasting reliable service. 5. Complete Seal Kit: The seal kit contains o rings of various sizes, 383 pieces in total, neatly sorted and comes in a plastic case for easy portability, easy to use. Specification: Item Type: O Ring Assortment Kit Material: Rubber OE: 4138938 Fitment: Replacement for Hitachi EX excavator. Package List: 1 x Rubber O Rings Kit1 x Storage Box