High-Security U-Lock with X4P Quattro Locking Mechanism Ensure maximum protection in medium to high crime areas with the standard PITBULL U-Lock. Featuring the innovative X4P Quattro Locking Mechanism, this lock secures the shackle on all four sides for enhanced security. Its robust 14mm (0.55'') hardened steel TriRadius shackle resists cutting, prying, and jacking, offering greater internal space for versatile locking options. The new crossbar and shackle coatings protect the finish, while the rounded design and centered keyway eliminate pry points. Additional features include co-molded crossbar cover, double rubber-coated shackle, all-metal end caps for impact resistance, and automatic keyway covers to seal against the elements. The Z-Cylinder is bump-proof and resistant to picking, pulling, or drilling, providing reliable security for bicycles and scooters.