Not every stop needs a kilogram of hardened steel. The Tether is for the quick errand — the coffee you are collecting, the shop you can see your bicycle from.
Honest about what it is
This is a deterrent, not a fortress. It will stop an opportunist walking off with an unattended bicycle. It will not stop someone with bolt croppers and time, and we would rather say so plainly.
Weighs almost nothing
At 340 grams it lives permanently in a saddlebag without you noticing, which means it is actually with you when you need it.
