E: Chrome Steel, Platinum plated A: Synthetic core, Aluminium wound D: Synthetic core, Silver wound G: Synthetic core, Silver wound A revolution in tonal sound and color for the discerning musician, Peter Infeld (PI) strings produce a rich spectrum of sound colors, the perfect blend of power and elegance, and a wide dynamic range. The strings deliver instant bow response as well as superior tuning ability. The soft left hand feeling brings out the best in you and your performance.