Should be 5.5 mm id. If your going to take the time and effort to replace the oem lines, go with oem new. you will be ahead in the long run. You can buy the individual lines that are a bit more spendy. I once had an oem yamaha part number for a 6' or so piece that was much cheaper, but I cant seem to find the part number at hand.
Since I am no longer associated with the local dealership due to an ownership change, I no longer have access to hard to find part numbers. Honda used the same size lines to feed the carbs so there is an avenue as well.