What is a hybrid string?
A set of hybrid strings uses kevlar or a similar, ultra-durable but stiff string for the main strings and a more resilient, less durable string for the cross strings. The crosses don’t need to be especially durable, because it’s the mains that take most of the abuse and are first to break at least 95% of the time. The more resilient crosses add springiness to the string bed, which with all-kevlar strings would be extremely stiff. The kevlar mains should usually be strung at a lower tension than the crosses because their greater stiffness would prevent the crosses from deflecting properly if both were equally tight.