4K-2039 is a Caterpillar O-ring seal molded in NBR with 75 durometer hardness, designed for hydraulic interfaces. It has an inner diameter of 12.42 mm and a cross‑section of 1.78 mm (standard size 14). This replacement seal is compatible with Caterpillar equipment and is associated with models including 515, 518, 525B, 525C, 525D, 528, and 535B, where it serves to prevent fluid leaks at sealed joints.
