Kryptonite Evolution Bicycle FlexFrame 3 25 Inch
I've been using this product for the last three weeks now and i can only say good about it.
I have to say the internal space to lock the bike (3.25" by 7") is a little bit small as it won't go around a large street poles, but if you manage to find a small street pole or a bike stand, it's extremely good as its less space for thieves to use a lever and be able to break the lock. It is pretty lightweight for this kind of lock, it feels solid and it works like a charm. The included Flex Cable is very useful to protect the wheels while locking only the frame with the lock. The little velcro on the Flex Cable has fallen, but i could re-sew it to the cable, but it's holding by itself so i didn't bother.
I also bought the Avenir Seat Locker (3mm / 2 feet) with this just to lock the bike seat to the Flex Cable as an added security.
Very good product as far.