OnGuard BullDog Series U-Lock - 3.5 x 5.5", Keyed, Black/Yellow, Includes bracket color-polarized-orange the Fly Nova BMX is

the Fly Nova BMX is a great choice

and 15 will ONLY work on flip-flop hubs

There is also a rubber o ring which protects the threads on the crank arms

37 x 24 thread per inch

OnGuard BullDog Series U-Lock - 3.5 x 5.5", Keyed, Black/Yellow, Includes bracket color-polarized-orange the Fly Nova BMX isOnGuard BullDog Series U Lock 3. 5 x 5. 5", Keyed, Black Yellow, Includes bracket OnGuard BullDog series u locks feature X2P Double Bolt lock mechanisms and strong 13mm (0. 51) hardened steel shackles for a full circle of protection. Bulldog includes free 1 year, anti theft guarantee 4. 6 Tons pull strength with anti drill and pick resistance Hardened ultra steel shackle with reinforced sleeve over crossbar and cylinder for added security 13mm