Yes you should be able to see the difference on weight forward line. The end that connects to the leader will have a few feet of smaller diameter line and then you will notice that the line will have a progressively larger diameter for a few more feet and then will taper off to a smaller diameter again. The end that connects to the arbor on the reel will have the same smaller diameter for most of the length of the flyline all the way up to the weight forward section (the larger diameter) of the line.