splint on 2 fingers same hand

what is the appropriate modifier used?

FA-F9 Fingers Modifiers

If you're asking about modifiers for the fingers, it would be as follows:
FA - Left Hand, Thumb
F1 - Left Hand, 2nd Digit
F2 - Left Hand, 3rd Digit
F3 - Left Hand, 4th Digit
F4 - Left Hand, 5th Digit
F5 - Right Hand, Thumb
F6 - Right Hand, 2nd Digit
F7 - Right Hand, 3rd Digit
F8 - Right Hand, 4th Digit
F9 - Right Hand, 5th Digit

If I am not interpreting your question correctly, you may need to explain more clearly. I am assuming here you are asking for anatomical modifiers?

re: FA-F9 Fingers Modifiers

Your information is incorrect! Modifers for fingers are as follows according to HCPCS 2012 coding manual: left hand thumb is FA, second digit F1, 3rd digit F2, 4th digit F3, 5th digit F4. Right hand thumb is is F5, second digit F6, 3rd digit F7, 4th digit F8, 5th digit F9.