Signum Pro’s Blackline power Tornado takes Co-polyester strings to a new level due to its new optimized molecular structure. Tornado is manufactured in an heptagonal shape which is then reheated and axially twisted. Blackline power Tornado offers players exceptional spin and outstanding power in combination with excellent playability and comfort without sacrificing durability. Tornado maintains Signum Pro’s legendary reputation for producing strings with minimal tension loss and string movement.