Master Hidden Shackle Lock - #6271N BUMP PROOF TECHNOLOGY BumpStop Advanced Cylinder Technology. This lock is also available without Bump Stop, search 6271KA in our store front. High security 6-pin cyclinder for maximum pick resistance. Removable cylinder for replacement or repinning. BOLT CUTTER TOUGH - fully shielded hardened stell shackle offers impossible to cut and pry resistance features. 2 keys included. The hardened diecast steel body is strong, durable and resists corrosion. Lock dimensions (see image) - A) 3/8 (10mm), B) 19/32 (15mm), C) 1-23/32 (44mm) Width 2-7/8 (73mm)