Medical Pediatric 0.5ml/1ml Gel& Clot Activator Non-Vacuum ... A plain pediatric 0.5ml tube is a small, non-vacuum blood collection tube used for microsampling, often with a clot activator for serum separation. It is designed for neonates, infants, and children to minimize blood volume loss, ensuring, for example, safe serum tests with only a 0.5ml blood volume.