A 3-pack of 47" long nylon with polyester core yo-yo strings in regular thickness.
From the ZipLine Strings website:
"These started out as a personal side project, but turned into another obsession. Whether or not you're into nylon strings, these will be a treat to at least check out. The addition of our poly core thread blend is a real game changer, as this type of poly adds just the right amount of density, and reduces the elastic properties of the nylon tread. What's all this mean? Well, simply put, these strings just perform a bit more predictably than if we were to use 100% nylon. The density and thickness are a bit more similar to our poly blends, and it's much less stretchy than you'd expect from nylon, while keeping much of the ultra whippiness that nylon is known for.
Why are these so expensive? Well, they are much more labor intensive to make and the material is nearly 71% more expensive than bulk poly. We just can't get away from this expense - it's painfully true."