metrial : Brass

use :

most conditions , if you are located 

in United State / Canada the water supply pipe size is G9/16 (9/16-24 UNEF)  

in Europe the water supply pipe size is G3/8,

in Brazil / China  the water supply pipe size is G1/2,

M=Male, F=Female ,price is for one pair/2pcs

  option M-9-16-F-3-8 : connect United State G9/16 hose to Europe G3/8 pipe

 option M-9-16-F-1-2 : connect United State G9/16 hose to G1/2 pipe

 option M-3-8-F-9-16 : connect Europz n . (n v ne G3/8m hose to United State G9/16 pipe

 option M-3-8-F-1-2 : connect Europe G3/8 hose to  G1/2 pipe

 option M-1-2-F-9-16 : connect G1/2 hose to United State G9/16 pipe

 option M-1-2-F-3-8 : connect G1/2 hose to Europe G3/8 pipe

here is the length of each size for reference +-0.3mm , if you still don't know how to select, please contact us