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.