New York Fahgettaboudit Chain

Kryptonite was founded in 1972 in Boston, named after the fictional mineral that could weaken Superman — the implication being that not even Superman could break the lock. The New York family is Kryptonite's heavy-duty top tier, named for the city that gave the brand its reputation for bike theft resistance, and the Fahgettaboudit Chain (the name is a Brooklyn pronunciation of 'forget about it') is the heaviest chain Kryptonite makes. It uses 14 mm six-sided links of 3T manganese steel — six-sided because the corners resist bolt-cutter jaws better than round links — paired with the New York Disc lock head, whose 15 mm hardened-steel shackle and hardened double-deadbolt mechanism are explicitly engineered to resist twist and pry attacks rather than cutting alone. It is rated Sold Secure Diamond in the UK (the top tier, alongside the Kryptonite New York Standard U-Lock) and Kryptonite's own 10/10 rating, the highest level the brand uses. It is heavy — almost 5 kg for the 100 cm version, ~6.8 kg for the 150 cm — which is the point. This is not a commuter lock; it is the chain you leave permanently chained to an anchor at home, or carry on a heavy e-bike or motorcycle.