Description The Cummins stainless steel marine coolant filler cap is a genuine OEM component for Cummins diesel engines using closed-cooling systems. Cross References/Supersedes: 3393978 Genuine Cummins filler cap for marine and industrial diesel engine coolant expansion or surge tanks. Durable stainless steel construction provides corrosion resistance in harsh marine environments. Used on various Cummins engine families, including 4B3.9, 6A3.4, 6B5.9, B6.7 CM2350 B121B, and ISB6.7 applications. Identified by NSN 2930-01-468-0786 and CAGE code 15434 for fleet and defence logistics.