* professional silent disco wireless headphones with 433mhz/863mhz/915mhz ism band, specific channels optional * transmits audio signal about 300m, through walls, floors and ceilings. * active noise reduction system for crystal clear sound * advanced 40mm speaker for outstanding sound performance * double pll system for ultimate frequency stability * auto mute and automatic shut-off after 10 minutes of no signal detection, conserve battery life * funky flashlights gently pulse on as you pump the tunes up * big channel-indicating logo light, you can see the channel difference by logo color * soft leatherette ear cushions, and robust headband let you listen to your entertainment in Extreme comfort, even during long hours of extended wear * endless headphones can be used simultaneously with one transmitter * multiple colors available for option 20pcs=1carton carton size:47.5*34.5*46.5cm