1992 GMC ( Astro Van)

I have a 92 Astro van and the brake lines went bad , I need to know if the lines comming out of the ABS system are the same ? I'm replacing the lines from the ABS system back and I'm haveing a hell of a time findind the sizes. I know the line going to the back brakes is bigger and it has a splitter in the rear of the van, but the front two lines comming from the ABS looks as if the sizes are diff, does anybody know ...