Item Type: Referee Whistle_x000D_ Material: ABS Resin_x000D_ Frequency: 0-4000Hz_x000D_ Weight: Approx.30g/1.1oz_x000D_ Product Size: Approx. 49x20x13mm/1.9x0.8x0.5in 1ABS resin strengthened whistle mouth, environmental protection material, cold and hot temperature resistance, stable and chewy. Whistle original mouthguard, prolong the service life. 2Applicable to various scenarios, basketball, football, volleyball games, traffic guidance, military training and so on. 3Adjustable nylon hanger, hanger easily through the tail hole, double ball fixed hanger length, not afraid of losing, not afraid of falling. 4High frequency boom, lightweight and portable. Considering that human ears are more sensitive to the audio of 1000?4000Hz, the treble frequency is set to 4000Hz. 5Two independent sound holes. In a volleyball match, the referee is located in the middle of the court. The professional volleyball referee whistle, and the sound can be transmitted to both sides. 1 x Whistle 1 x Lanyard 2 x Mouthguard