SR515 DSMR 5 CH Receiver
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Product Specifications: 

# of Channels:  5
Modulation:   DSMR/DSM2
Band:   2.4 GHz
Length:   1.28 in (32.7 mm)
Width:   0.84 in (21.4 mm)
Height:  0.53 in (13.6 mm)
Weight:   0.21 oz (6.0 g)
Voltage Range:   3.5-9.6 V
Antenna Length:   ​4.72 in (120 mm)

Manual: 

​https://www.spektrumrc.com/ProdInfo/Files/SPMSR515-Manual-EN.pdf​