This duo cone seal (also known as a floating or toric seal) pairs precision-machined steel rings with a Nitrile rubber toric ring to keep dirt, mud, and water out while retaining lubricant in heavy equipment components such as final drives, track rollers, idlers, and wheel hubs. Cross-referenced to Caterpillar part number CTC-9S3521 for a confident fit. Material: Steel / 65A NBR.