The HiBore was the first golf club to re-think the traditional shape of a driver head. For the first time, the geometry of the head itself was optimized for performance (the crown was dropped halfway to the ground), leading to dramatic gains in driving distance and straightness. Material thicknesses were optimized through many iterations of impact simulations, stress analysis, and new manufacturing methods. Additionally, sound and feel were dramatically improved through extensive vibration analysis and simulation, to ensure the perception of the club on the course matched the improved performance level.
This all combined to make it the #1 selling driver on the market in 2007, and led the way for a wave of "geometric drivers" over the following years. It was used by a number of professionals on the PGA tour, including Vijay Singh, who was ranked #1 in the world while using it.