| 摘要 |
A tennis racket frame ( 10 ), including a sleeve composed of a fiber reinforced resin, having a weight not less than 180 g nor more than 270 g, when strings are not mounted in a ball-hitting face thereof surrounded with a head part thereof. Supposing that the strings are not mounted in the ball-hitting face, a secondary natural frequency (F 1 ) of the racket frame in an in-plane direction thereof is set to not less than 200 Hz nor more than 320 Hz, a secondary natural frequency (F 2 ) thereof in an out-of-plane direction thereof is set to not less than 480 Hz nor more than 650 Hz, and F 1 /F 2 is set to not less than 0.3 nor more than 0.6.
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