Question about Corsair Premium individually sleeved

Yes, the premium cable with part number CP-8920243 is compatible with your HX850i as it is designed for all Corsair Type 4 power supplies. According to the manufacturer, the HX850i uses type 4 cables, as confirmed in the official compatibility lists. The PCIe cables with a length of 65 cm and individual connectors therefore fit without any problems. For additional security, you can consult the compatibility list on the Corsair website.