The FrSky Zipp 9 is the 900MHz high-gain antenna which has the stronger signal and longer control for the directional range. It works compatible with all FrSky 900MHz R9M modules and new coming modules.
 
This is a 3dBi improvement over the stock antennas both internal and external that come with your transmitter. 
 
Specifications
Frequency Range: 860~880MHz / 902MHz~928MHz
Peak Gain: <4.29dBi (868MHz) / <4.68dBi (915MHz)
S11: <-10dB
Input Impedance: 50Ω