I was watching some of Hal Ruzal's lock grading videos, and noticed several times him praising these U-locks where the shackle has a square cross section instead of round, and it makes sense. I can see how that can resist bolt cutters. However I didn't see anything like that from Kryptonite, at least not when I last looked. Who makes locks like that? Onguard Locks don't have them, either.

Blackburn makes locks with hexagonal cross sections:

https://www.blackburndesign.com/locks.html

I think he's using an Abus Granit in that video. Great lock, usually rated around the same as Kryptonite's New York Standard U-lock in terms of strength. But it's way lighter, giving it one of the best strength-to-weight ratios (maybe tied with the Evo Mini), and I hear far fewer complaints about keys snapping or the lock mechanisms seizing up. (Probably still a good idea to do lock maintenance though.)

Try looking around the different online bike resalers, I wanna say I saw it for like $80 plus shipping somewhere. Could be remembering wrong though. BTW, there are different versions of the Abus U-locks, some in the Granit series and some not. But the one I linked in Amazon I use and love.

As the cherry on top, it comes with an awesome mounting bracket. Don't know how many people I've heard say their stock Kryptonite or OnGuard mounting bracket is craptastical. No wonder people are buying 3rd party carriers like the Twofish one. But you won't need one with that lock.

Wish I could pick it up mate, but just can't do it at this time. To tell the truth it's pretty rare that I ride anywhere that I need to lock up and leave the bike, right now anyway. I was really just more curious than anything else for when I do look into getting some good locks.

i wouldn't be too concerned about square cross-sections on a U-lock. anything that can bust open an NY-3000 or NYFU lock can bust open a comparable lock with a square cross-section.

with chains, square cross-sections are generally used in security chains that are made to be difficult to cut, but NOT made for lifting or pulling. that's why they cut "normal" chain at the hardware store with a bolt-cutters, but it's harder to find hardened chain by the foot. that said, not all square cross-section chains are equal.