Buyers must prioritize OEM compatibility codes (e.g., 0445 series for Bosch/Man) and material composition. Ensure the nozzles are made from high-grade alloy steel or high-speed steel (HSS) to withstand extreme pressure and heat. Key parameters include the spray hole diameter (precision to microns), opening pressure settings, and needle valve lift. For heavy-duty Man engines, verify that the nozzle tip has undergone vacuum hardening or DLC (Diamond-Like Carbon) coating to enhance wear resistance and prevent carbon buildup.