When sourcing active RFID tags, the frequency range (typically 2.4GHz or 433MHz) is critical as it determines the read range and penetration through obstacles. You must verify the battery life expectancy, which should ideally be 2 to 5 years depending on the ping rate. Additionally, ensure the read range meets your specific requirements, often reaching up to 100 meters in open areas. For wearable applications, the IP67 or IP68 waterproof rating is non-negotiable to ensure durability against sweat and water immersion.