For the Factory firmware and BF3.5.7 firmware, please use the bellowing Diff
Sailfly-X Frsky version DIFF for original Factory firmware and BF 3.5.7
Sailfly-X Flysky version DIFF for original Factory firmware and BF 3.5.7
Sailfly-X DSMX version DIFF for original Factory firmware and BF 3.5.7
Sailfly-X No RX version DIFF for original Factory firmware and BF 3.5.7
For the official Betaflight firmware v4.0.0 or v4.0.1 or v4.0.2 and latest, please use the bellowing Diff
Sailfly-X Frsky version DIFF for BF 4.0.2
Sailfly-X Flysky version DIFF for BF 4.0.2