Multi-purpose: strap a jacket to your pack, use as a handle for carrying broken bags, organize cords and devices, mold into a stand for watching videos on your phone, etc.
3, 6, 12, 18, 24 in.
[exterior] rubber, [interior] wire
yes, 24 in. only
I swear by these gear ties. I've used them for anything from keeping my charging cables organized to strapping a jacket to the outside of your pack and even as a make-shift handle for awkward items (I recently fastened the 24 in. cord as a replacement handle for a case of beer we brought backpacking). Bottom line: get some and thank me later.
Tip: Be sure to get the Clippable Gear Tie with the S-Beaner. It's great for larger items and the S-Beaner comes in handy for anything from securing your water bottle to clipping packing cubes to the outside of your pack.