The engine assembly w/ o-ring (R0837200) are replacement parts that are made by Polaris. They used the same high-grade materials that were used to make the original factory parts. Making them genuine OEM parts that all our customers can trust. The engine assembly w/ o-ring (R0837200) are replacement parts that are made by Polaris. They used the same high-grade materials that were used to make the original factory parts. Making them genuine OEM parts that all our customers can trust.