Master Lock Pro Series (4) Hidden Shackle Padlocks Keyed Alike

In this review the Master Lock Pro Series 6271KA-4 is evaluated as a heavy-duty keyed alike padlock pack for commercial and industrial use. The bottom line is simple: if you need four identical, high-security padlocks with concealed shackles to protect trailers, vending, or outdoor equipment, this pack delivers robust physical security and convenience with eight keys included. The review highlights fitment considerations and real-world durability so buyers know when these locks are an appropriate choice.

Key Features

• Hidden shackle design: The lock body conceals the 3/8 in hardened boron alloy shackle, reducing leverage points and improving resistance to cutting and prying.
• Keyed alike convenience: All four padlocks open with the same key, allowing a single key to manage multiple locks and simplifying access for teams.
• Heavy duty construction: The reinforced 2-7/8 in zinc die-cast body provides rugged protection against outdoor conditions and impact.
• Pick resistant cylinder: A re-keyable 6-pin cylinder with spool pins raises the difficulty of picking while remaining serviceable for rekeying if needed.
• Clear fitment guidance: The product includes dimensional guidance for hasp fit and a schematic so buyers can check that the shackle will engage their latch.
• Lifetime guarantee: The manufacturer backs the lock with a lifetime guarantee, offering long-term confidence in the purchase.

Who It's For

These padlocks suit fleet operators, contractors, and owners of cargo trailers or vending equipment who require multiple locks that share one key and need protection against bolt cutters and casual theft. The concealed shackle and hardened boron alloy make them a solid choice where exposed shackles would be vulnerable.

Shoppers who have unusual or oversized hasps should check the provided schematic and measure the center distance and hole depth before buying; some enclosed trailer latches may be off-center and prevent the pin from engaging. If you need locks guaranteed to be keyed alike across multiple separate multi-packs, order the single 8-pack option rather than two 4-packs.

Pros & Cons

Pros

• Excellent physical security thanks to a fully shielded shackle and hardened boron alloy construction.
• Convenient keyed alike setup with two keys per lock, totaling eight keys for the pack.
• Solid build quality and good value for buyers needing multiple heavy-duty locks.

Cons

• Not guaranteed to be keyed the same if you order two separate 4-packs, so larger orders require the 8-pack for consistent keying.
• May not fit all trailer hasps; requires measuring hasp hole center and depth to confirm fitment.

Specifications

Pack quantity	4 padlocks, keyed alike
Keys included	8 total keys (2 per lock)
Body width	2-7/8 in (73mm)
Shackle diameter	3/8 in (9mm) hardened boron alloy
Shackle dimensions	A 3/8 in (9mm) B 19/32 in (15mm) C 1-23/32 in (44mm)
Cylinder	Re-keyable 6-pin with spool pins
Warranty	Lifetime guarantee

Our Verdict

The Master Lock Pro Series 6271KA-4 is a practical, heavy-duty choice for anyone needing multiple keyed alike padlocks with concealed shackles and strong resistance to cutting and prying. It represents good value for commercial and outdoor use, provided buyers verify hasp fitment and order the correct pack size when identical keying across many locks is required.

Frequently Asked Questions

Will two separate 4-packs be keyed the same?
Not necessarily; if you need eight locks keyed the same, purchase the 8-pack option to ensure identical keying.

How do I check fitment for my trailer latch?
Measure the hasp/latch hole center distance and depth against the provided schematic; if the hole center is more than 13/16 in (20mm) from the edge the lock pin may not engage.

Are these padlocks weather resistant?
The reinforced zinc die-cast body and concealed shackle offer strong outdoor durability and protection from cutting and prying for typical external applications.