FEATURING BumpStop TECHNOLOGY - Lock bumping a surprisingly simple method of breaking in through locked doors and padlocks - is undoubtedly the newest emerging threat to personal property security. And virtually all locks in use today are particularly vulnerable to bumping. Until now. BumpStop Advanced Cylinder Technology employs an innovative, patent pending design which utilizes a unique reverse rake tapered driver pin, high performance springs and tightly machined cylinder chambers. During a bump attempt, this design prevents the transfer of force from the bump key to the pins and therefore blocks rotation of the cylinder so that the lock remains locked.inquire and we can normally have them in a couple of days.This listing is for four (4) High Security Keyed Alike Padlocks w/ 8 keys. ProSeries Padlocks are designed for Commercial/Industrial applications. Limited Life Time Warranty. ATTENTION: If you order two 4-packs they will NOT necessarily be keyed the same. To ensure you get two 4-packs keyed alike, you must order the 8-pack.Ideal for harsh outdoor conditions - exclusive Pro Series Weather Tough cover protects lock from water, ice, dirt and grime. Solid iron shackle shroud resists harsh physical attacks. The removable cylinder can be replaced or re-pinned. 5 spool pin tumbler cylinder for added pick resistance. Dual ball bearing locking mechanism resists pulling and prying.These locks feature the BumpStop Advanced Cylinder Technology. (for explanation see more product details below).DIMENSIONS: 2-1/8 (54mm) wide heavy steel body, each weighing 1.55 lbs. A 5/16 (8mm) diameter hardened boron alloy shackle with 3/4 (19mm) inside height clearance.Solid iron shackle shroud resists harsh physical attacks. The removable cylinder can be replaced or re-pinned. 5 spool pin tumbler cylinder for added pick resistance. Dual ball bearing locking mechanism resists pulling and prying.