The Tecnifibre 305 17 Gauge SPL string uses Silicon Pyrogene Lubritec, SPL, technology that reduces elongation and improves durability by 40%. Also, its micro-composite fibers provide high resiliency for increased power, while the polyurethane in the string reduces shock during ball impact. Thin gauge for excellent ball speed. Tecnifibre 305 17 | Green | Christy Sports