Buyers must verify that the machine meets CE, ETL, or UL certifications to ensure electrical safety and food-grade standards. Key specs include hopper capacity, cylinder volume, and pre-cooling functions which keep the mix fresh overnight. For soft-serve machines, check the overrun rate (the amount of air whipped into the mix); high-end pumps can achieve 30-60% overrun, significantly increasing profit margins per serving. Ensure the body is made of SUS304 food-grade stainless steel for durability and hygiene.