The In-Line Groove Lead allows you to wrap your leader around the lead without it ever getting damaged.
Previously, this 'around-the-outside' system left the leader exposed to getting bashed against the lake bed on the cast, but the In-Line Groove Lead removes the possibility and even enables you to fish a drop-off lead with straight main line or fluorocarbon.
When used in conjunction with a Drop-Off Stem, this really is an incredibly safe and effective tactic.
This setup is best used in weedy or snaggy situations, and will help you put more fish on the bank. Without a lead in the way, it's a lot easier to get carp to the net. So give it a whirl. For this type of fishing scenario, it's absolutely ideal.