Notch filters are designed to knock out specific bands of radio interference. They have significantly lower loss than high pass, low pass, or band pass filters and often have higher than 20db choking capability.
The 1.3/2.4GHz filter is used on your 1.2/1.3GHz video transmitter when flying on 2.4GHz control.
Specifications:
Passband: 1220-1360MHz
Reject Band: 2300-2550 MHz
Filter strength: 26db