hand-cuff lock!
 

havnt seen these anywhere before
http://i148.photobucket.com/albums/s13/57tony/cuff.jpg
http://i148.photobucket.com/albums/s13/57tony/cuf.jpg
• Ratchet cuffs provide snug, secure fit no room for jacks and bars
• 76mm diameter cuffs allow locking to forks, frames, signposts and parking meters
• Pivoting Link prevents a fixed anchor point, taking away the use of leverage to defeat them.
• Hardened laminated steel construction with hardened pivot links for optimum cut & pry resistance
• Compact and Easy to Carry - fold in half to fit in a seat bag, backpack or pocket
• 10-pin Tubular Cylinder - pick and drill resistant and easy to use.
• 54mm long for convenient locking
• Lifetime Guarantee

looks pretty cool but dont know if id trust it
it'd be handy as an extra wheel to downtube lock

They are expensive, heavy, and vulnerable to the bic pen defeat.

But I still think they are pretty cool.

nice idea, i think the link can be cut with bolt cutters quite easily though.

houdini theft.

I wonder if the links can be defeated with a chain tool.

No you gotta get a sense of scale. those things are huge. The cuffs are designed to go around a parking meter post, and the links are more like a motorcycle chain than a bike chain.

I have seen them popped apart with a big screw driver they changed the key so bic doesn't work any more
if you are gunna spend the money get two mini u locks or a nyc chain and an american padlock

you can twist em and snap them with the leverage of the bike

s&m.

I saw a bike locked up with those a few days ago. Well, I saw a frame locked up with them. Everything else was stripped. The only things left were the headset and bottom bracket.

Free headset and bottom bracket!

I'm allergic to those.

I have had one for about 4 years now. Lock my bike up all over the place and never had any issues. I was worried about the bic pen thing too, but the company says it is not vulnerable. I am sure there are ways to defeat it, but so far it has been the most successful lock I have used.

They're crap. Easy to break, easy to pick and the company won't acknowledge that they suck.
Of course they're going to say that. I for one will never buy another product for that half assed good for nothing ****box of a company as long as I live. Check out my experiences with Crapster Crock

I have the black ones, but don't use them anymore. I don't know if I buy the 'break them with leverage from the frame'. These things are burly. I think you're bike tube would crimp before they'd break. However, the tubular lock thing kills it for me, as does master locks response to the issue ("there's no problem...").

Also, the keys are a super soft brass (or were when I got mine). I wore through both keys in one year of medium use. ML will replace them for free, but it's a PITA.

In the end, I found them only marginally more convenient than a chainlock. I'm way way way happier with my onguard pitbull mini-u.

When I was shopping for new locks, these came up and got very, very poor reviews on multiple websites. I'm also in the "get 2 mini-u locks camp." I couldn't be happier with my 2 OnGuard Pitbull Minis.

I went and read through your experience with Master Lock. Sounds like the customer service really sucks. Would have been nice if someone would have actually posted a video of it being defeated. I have had 2 kryptonite locks (non-barrel key) defeated. And as I said I have never had my cuff lock defeated. I hope it never happens and I will probably end up getting a new lock later this year, but so far so good, and I consider 4 years pretty good in my city.

My friend has a pair. I never liked them because they limit your locking option. They are only good for shananigans.

Look, those circular key locks are easy to pick. All of them.

Since you asked, here's a crappy webcam vid of me picking my own MasterLock U pretty briskly:
http://cyrex.axio.hu/bb/video/masterlock.wmv

There is a guy by me who has one that has a taser that inserts into the lock area so anyone trying to pick it gets electrocuted...kind of cool.

Kind of illegal as well, and kind of dangerous for curious children, don't you think?

To the doubters...

I've broken a set of these in the name of product testing. Scary easy to break the center chain links. Imagine bending a bicycle chain the wrong way, against the links.

Thanks a LOT for that link, and your effort to right MasterLock's wrongs. I learned a lot reading that thread.

WOW. that thread is 3 years old, and they are still selling those??? Weird.

Keep a spare key in your butt, just in case.