Features:_x000D__x000D_High quality physical experimental instrument, durable and practical. _x000D_Two tuning forks of the same efficiency are made of the whole 45# carbon steel. _x000D_The edges and corners are neat and the surface is chrome plated, the frequency is 440 cycles per second. _x000D_The tuning fork set is used to demonstrate the resonance of sound in school. _x000D_Can be used as a general tuning fork of a variety of experiments, such as the sound of the occurrence, interference, sound conduction of various substances. _x000D__x000D_Specification:_x000D_Condition: 100% brand new_x000D_Frequency: 440 cycles per second_x000D_Fork section size: 6.5 * 16mm / 0.3 * 0.6in _x000D_Tuning fork arm length: approx. 109mm / 4.3in_x000D_Distance between arms:17mm / 0.7in_x000D__x000D_Package List:_x000D_2* Tuning Fork_x000D_2* Wood Resonator Box_x000D_1* Knocker_x000D__x000D_Note:_x000D_1. The tuning fork should be protected from breaking and high heat to prevent frequency change._x000D_2. The tuning fork and the sound box should have a reliable connection and should not be shaken when the tuning fork is inserted or removed. 1High quality physical experimental instrument, durable and practical. 2Two tuning forks of the same efficiency are made of the whole 45# carbon steel. 3The edges and corners are neat and the surface is chrome plated, the frequency is 440 cycles per second. 4The tuning fork set is used to demonstrate the resonance of sound in school. 5Can be used as a general tuning fork of a variety of experiments, such as the sound of the occurrence, interference, sound conduction of various substances.