When evaluating a Spa With Overflow Factory, prioritize the shell material, typically Aristech Acrylic reinforced with fiberglass and resin, to ensure UV resistance and durability. The overflow grating should be made of high-grade ABS or stainless steel to prevent corrosion. Ensure the filtration system includes a sand filter or high-capacity cartridge filter combined with an ozone generator or UV-C sterilizer for superior water clarity. Additionally, verify that the pumps are high-efficiency (CE/UL certified) and that the insulation uses high-density polyurethane foam to minimize heat loss.