The Kryptonite Keeper 785 is a very good lock, especially as a secondary. I have to admit I often use this chain (7mm four-sided chain links made from 3t manganese steel) as my only lock… so far so good. Knock on wood.
During our stay in Bisbee, where bike racks are nonexistent, the lock came in handy because we could lock to railings and trees otherwise not reachable by a U-lock. Bisbee is a pretty safe town, so the lock provided peace of mind for us and was mostly a deterrent for shitty bike-thiefs. Don’t know if the bikes would have fared well with this lock as the only form of protection overnight in Tempe, for example. But in places such as Tempe, I love having the chain as extra protection… a good way to secure lose parts such as my rear wheel.
There have been times, even on Mill Ave, that I have used this chain as my only lock and so far so good… but I consider myself extremely lucky and try not to leave my bike on Mill with any lock if I can avoid it…
The Kryptonite Keeper 785 is also great for the “bike pile.” You know, when you pile a bunch of bikes together for extra protection… or because someone forgot their lock. The chain can snuggly wrap around three top tubes. And because the chain is covered in a weather-proof nylon sleeve, no scratchies!
The end of the chain that goes in the lock is different from other chains I’ve seen, in that it ends in a “U”. From the Kryptonite website “Patent-pending end link design secures chain to hardened deadbolt eliminating critical vulnerability.”
It’s easy to transport and easy to use, if you know how to properly lock your bike.
The price is right, in the low $30s in Amazon.