IsoSpeed Professional (also known as "Professional Classic") is a polyolefin multi-filament string. Its characteristics are softness similar to natural gut and moderate power for a multi-filament string. I believe it's a good combination of softness and control. It's gentle on the arm even with high tension (58-60 lbs). Recommended for those who prioritize protecting their arm while seeking as much control as possible! I have 5 sets available, so please comment with the quantity you want if you'd like to purchase multiple sets. A small discount will be offered for multiple purchases. Brand: IsoSpeed Length: 12m Gauge: 1.2mm Color: Natural Country of Origin: Austria String Tennis String Poly Polyester Wilson Babolat Head Yonex Type: Tennis String Use: Hard Court