Abstract: A golf club head of an improved aerodynamic design, which includes deep cavities for airflow stabilization. Adjacent rims of these cavities meet to form a central rib. Cavities can be joined at both ends of the rib to form a continuous cavity or can be separated along their entire length to create two different cavities and in either case run parallel to the edges of the rear face. The cavities accommodate air turbulence and swirl, and the centrifugal force produced by the swirl in those cavities in the head imparts a thrust upon it which thus minimizes drag and maximizes the force with which it strikes and drives the ball. The cavities also minimize undesired aerodynamic vibration in the golf club so as to enhance the player's accuracy.

Abstract: A golf club (1), with a head or putter for the specific function of putting, which includes a front face with a negative inclination; a middle section (3) inclined approximately 45.degree., a section which acts as a mirror with a view to lining up the stroke; an inclined edge (22) which comes from the top end of the inclined face, of the base or of a horizontal surface continuing from the inclined one, with the peculiarity of altering the angle of the said inclination.

Abstract: A device to measure the tension of the stringing of rackets used for playing tennis, squash, etc. which entails an end area to strike the said stringing and another adjacent area which includes a multiple diapason or tuning device. On striking the stringing, and depending on the tension of the strings, one tooth of the multiple diapason vibrates, thus providing a signal which can later be measured or digitalized to provide a measurement of the tension of the stringing.