Kool Leadin is a lightweight, retractable, 2 metre dog leash/lead. It's pocket size. Even for small pockets. Yet it's strong enough for a pretty big dog.
How? Well, we went back to basics and took apart a few retractable leashes. Actually, we took apart every leash we could find.
And they were all designed the same way. When your feisty and energetic dog decides to pull, all of the load gets taken onto the steel retractor spring.
So you have to have a big, sturdy spring, in a large and heavy casing. Ugh.