Years back I used a piece of inner tube but now pull my leaders through a doubled piece of treated leather. If my memory serves me right, this leather straightener was once a Cortland accessory product. However I've found that any kind of straightening method I've used was only temporary. Also, the more I use that leader, the less likely the coils can be removed. I've used everybody's knotless tapered leaders and they all become like a corkscrew in the upper section tapering from the butt to the tippet. I'm the type who puts on a new leader when I replace a fly line and I just keep rebuilding it as necessary. I fish hard and often and don't believe it should be necessary, or is cost-effective, to replace the leader every other week or so.