The 0.7 gauge makes these strings incredibly durable.
The 0.7 gauge provides a good balance of durability and power.
The multifilament resin gives you better control over the shuttlecock.
The gauge corresponds to the string's diameter. A thicker string is more durable, but provides less feel. On the other hand, a thinner string provides more feel but is also more fragile and breaks more easily.
String gauges range from 0.75 mm (very durable) to 0.66 mm (very thin)