Unfortunately i did not find a detailed explanation for how to use reflection file editor (GUI) i just want to know if i am right and i have a questions about how it works as well 1- if i have 2 myfile-data.mtz files (for the same structure but 2 different ligands, one of them 1.9 A and the other 1.6 A) and i want to copy free set from one to the other. so i have in the (ALL Input Arrays) 2 intensity and 2 R-free flag. so what i did is to add in the (output array) one of the intensity which belongs to one and one R flag which belong to other. i was not sure how to use the other output options??? what should i check or uncheck in this particular case??? 2- How this works? suppose i have h k l (6 7 21) has flag 1 in the data.mtz file (the one i used to copy the free set to other mtz), if i will copy this to other mtz (which has no R flag of course), the program will look for (6 7 21) h k l in the other mtz to give it also flag 1. Am i right.??? 3- if i am right in number 2, Suppose the other mtz has no (6 7 21) h k l what will happen? if it is just ignoring it or assign flag 1 for other h k l which did not exist in the first data.mtz.this means it is impossible to get 100% free set similar between say the 2 mtz files in this case. thank you in advance thank you Dr Pavel and Dr Georg for your reply to my previous query TK DawoD