PB Shipping API Carrier Services

Carrier Service ID
Express Mail International 989
First Class Mail 980
First Class Mail International 987
First Class Package International 988
Ground Advantage 948
Ground Advantage Returns 949
Library Mail 986
Media Mail 985
Priority Mail 981
Priority Mail Express 982
Priority Mail International 990
Priority Mail Return Service 914

See full PB Shipping API (CarrierID=106) Reference.