Weight Stabilizing - Granules
(documented or estimated)
Mark 77 "Rassel"-Racket
The original Mark 77. Rattle Racket. "Most ball acceleration of any racquet I've tested." Racket Report Tennis-Magazine, July 77. Frame: Nylon shuttle with lead balls. Kübler + Co., D-7700 Singen
Due to the granules in the core of the racquet, the pressure of the centrifugal weight was optimally increased when swinging out, and during the stroke movement.