This is a complete system for secret two way talking. This Neckloop is having two SIM slots and having Volume regulatory buttons for better sound quality as per need of the user. 
 
Key Features -
8 Hours of battery backup 
2 days of standby 
On/Off button 
Volume + / - button 
two SIM cards at the same time 
75 dB mic - ultra sensitive 
auto call receiving function
Double antena
 
Cautions - 
Don't use this earpice for longer time. 8 to 9 hrs is maximum use time since it's electromagnetic ways might harm if exposed for longer durations. 
Never sleep with earpiece in your ear
Do not insert forcefully. Don't push the earpiece as they might harm your ear canal/drum. 
The buyer shall not use the product for any illegal purposes and shouldn't permit anyone to use the product in any kind of unlawful activities. We promote our products for betterment for our lives not to go against law, or humanity.