The Head CT 135 squash rackets feature the Metallix strengthening material that is applied at the key stress points around the corners of the heads to reduce torsional twist and frame breakage, while the Microgel frames ensure lightweight but torsionally stiff heads.. Similar in design to the 115 CT frame, these slightly heavier rackets offer the user more feedback from every shot, more durable frames, and a little more control than the raw power of the lighter weight frames. Additionally, the latest corrugated technology shaft design ensures up to 12% extra stiffness and maximises the transfer of swing speed to the ball.