What parts are included in a Cummins injector cup replacement kit? A proper injector cup kit contains more than just the metal sleeve. A complete kit typically includes: The injector cup (sleeve) – Usually made of hardened steel or stainless steel. Upper and lower O-rings (or copper seals) – These seal the cup to the cylinder head coolant passages. Never reuse old seals. Installation lubricant – Required to prevent O-ring cutting during insertion. Retaining compound (sometimes) – Used on threaded cup designs to prevent loosening. Some engines (like older N14 models) use a threaded cup with a copper sealing washer instead of O-rings. Always verify your engine serial number (ESN) before ordering because cup designs changed multiple times over production years. https://www.cq-longshine.com/cummins-injector-cup