For internally routed bikes, this tool is a godsend. True, with a lot of patience, and often, a little luck, you can run your cables internally without this tool. The thing is this tool takes all of the patience and luck out of it. You just run the leader through with the magnet, attach the cablehose to the leader, and pull it through. Total frustration-saver!
Did a bunch of research on different cable routers and this looked most inclusive. It was a little more pricier but you can count on Park Tools performance and quality. Worked great and have options for all types of routing.