Complete starter set for in-ear monitoring. Includes (1) XSW IEM SR transmitter, (1) XSW IEM EK Receiver, (1) IE 4 In-Ear Headphones, (1) XSW Rack Mount Kit, (1) NT 12-5 CW power supply with power adapters, (2) AA batteries, frequency range: C (662 - 686 MHz).