Used for wireless transmission for instruments 
 
*PRICING IS PER ONE UNIT*
 
Key Features
For Use with XSW-D Wireless Mic System
1/4" Plug Output Connector
For Electric, Acoustic, Bass Guitars
Easy to Use, Plug & Play Operation
Lightweight Miniature Housing
Low Latency for Tighter Performance
USB-Rechargeable 5-Hour Battery
Includes USB Charging Cable
5 Systems at Once Max, Up to 250' Range
B&H Link: https://www.bhphotovideo.com/c/product/1444561-REG/sennheiser_xsw_d_instrument_rx_xs_wireless_digital_receiver.html