There are three primary technologies: Thermoelectric (Semiconductor) cooling, Compressor cooling, and Passive Gel-pack cooling. For B2B buyers, Thermoelectric coolers are the most popular due to their compact size and precise temperature control (2-8°C). If your customers require long-distance travel without power, prioritize Passive Vacuum-Insulated flasks which can maintain temperature for up to 48-72 hours. For high-end medical use, Compressor-based portable fridges offer the most stable cooling but at a higher price point and weight.