The O-ring K 27411 is specified as the sealing element for parts K 27402 and K 27403, providing fluid-tight joints in the starting-valve subassembly of the Sulzer ZV40/48. Typically made from a chemical- and heat-resistant elastomer, this O-ring prevents oil or hydraulic fluid leaks that would degrade valve response or contaminate adjacent components. Because O-rings are wear items, keeping spares and replacing them whenever seals show hardening, nicks or compression set is a simple, high-value preventative measure to maintain reliable engine start and valve integrity.