About this item
The BEST 21B722 is a solid extruded brass body padlock with a 5/16-inch diameter stainless steel shackle, 1-1/2-inch shackle height, dual heel and toe locking, 7-pin SFIC housing, sold less core. If you searched "shackle diameter padlock", "padlock shackle diameter", "padlock shackle sizes", "padlock diameter", or "standard padlock shackle diameter" - this page answers all of those questions and explains exactly where the 21B722 fits.
Padlock Shackle Diameter: What It Means and Why It Matters
This is the question behind every one of these searches, and no competitor product page for any padlock answers it directly.
The shackle is the U-shaped metal loop that passes through the hasp, chain link, door loop, or cable being secured. Shackle diameter is the cross-sectional thickness of that U - how thick the metal rod is. A thicker shackle is harder to cut with bolt cutters, harder to saw through, and harder to attack with freeze spray and impact.
Here is the practical guide to BEST B Series shackle diameter options:
1/4-inch diameter (11B series): The smallest BEST B Series shackle. Fits narrow hasps, thin chain links, and applications where clearance is tight. Lower resistance to cutting than larger diameters. Correct for indoor, controlled-access applications where physical attack resistance is not the primary concern.
5/16-inch diameter (21B series - this listing): The mid-range BEST B Series shackle. This is the most commonly specified diameter across institutional applications - it threads through standard commercial hasps and door loops without clearance issues while providing meaningful cutting resistance. The BEST 21B722 shackle meets ASTM F883 Grade 4 for attack resistance.
3/8-inch diameter (41B series): The largest BEST B Series shackle. Maximum cut resistance in the B Series. Used when the application is higher-risk, where bolt cutters are a realistic attack concern, or where hasp and chain dimensions allow the larger diameter.
If your hasp opening, chain link, or door loop accommodates a 5/16-inch shackle, the 21B722 is the right specification. If it's tight, the 11B (1/4-inch) may be necessary. If clearance allows, consider the 41B (3/8-inch) for higher attack resistance.
Standard Padlock Shackle Diameter: Where 5/16" Fits
The 5/16-inch diameter is the most widely deployed shackle diameter in institutional padlock systems - schools, hospitals, utilities, government facilities, and commercial campuses. It fits standard 7/8-inch hasp slots, standard commercial door loops, and most industrial equipment lockout hasps. When someone searches "standard padlock shackle diameter" for commercial or institutional applications, 5/16-inch is the answer.
The BEST 21B722's 7/8-inch shackle opening width means the padlock can pass through hasps and chain links with up to 7/8-inch inside opening - a standard dimension for commercial hasps and most equipment lockout points.
21B722 Model Decoded
21B - 21B Series: brass body, 5/16-inch shackle diameter. The "2" prefix identifies the 5/16" shackle diameter within the B Series family.
7 - 7-pin SFIC core housing. Accepts all BEST 7-pin SFIC cores.
2 - 1-1/2-inch shackle height. The shackle height options in the 21B series are: 3/4" (21B72), 1" (21B711), 1-1/2" (21B722 - this listing), 2" (21B772), 4" (21B782).
Less core - Ships without an interchangeable core installed. The 7-pin SFIC housing is ready for your core, but the core must be ordered separately. This is correct when the padlock is being added to an existing BEST key system - you order the core keyed to your system from your BEST distributor and install it into the padlock.
Dual Heel and Toe Locking: Why It Matters
Most consumer-grade padlocks lock only at the heel (the short end of the U). Single-point heel locking means an attacker can use a spreader - two metal bars forced into the shackle opening from either side - to pry the shackle out of the body by pulling upward on the toe side.
The BEST 21B722 locks at both heel and toe. The shackle is held at both ends of the U when the padlock is closed. A spreader attack against the toe is blocked because the toe is positively locked in the body. This doubles the force required for a spread attack and eliminates the single-point failure of heel-only locking.
SFIC Less Core: Adding This to Your Key System
The 21B722 ships as "less core" - the SFIC housing is empty. To put this padlock into service, order the appropriate BEST 7-pin SFIC core keyed to your facility's master key system from your BEST distributor. The interchangeable core drops into the padlock housing and is retained by the control key. When the padlock needs to be rekeyed - after a key loss or personnel change - pull the core with the control key, install a new core, and the padlock responds to the new key. No new padlock purchase, no disassembly, no locksmith visit to the padlock.
This is the core reason BEST B Series padlocks are specified for institutional and government facilities. The padlock body lasts for decades. The security can be updated in seconds.
Specifications
Model: BEST 21B722
Series: B Series / 21B Series
Body: Solid extruded brass
Body Dimensions: 1-25/32" x 2-1/16" x 13/16"
Finish: 626 Satin Chrome (standard)
Shackle Material: Stainless steel
Shackle Diameter: 5/16" (8mm)
Shackle Height: 1-1/2"
Shackle Opening Width: 7/8"
Shackle Locking: Dual heel and toe
Core Housing: 7-pin SFIC - less core (ordered separately)
Compatible Cores: All BEST 7-pin SFIC cores - keys into any BEST master key system
Shackle Heights Available (21B): 3/4", 1", 1-1/2", 2", 4"
B Series Diameter Options: 1/4" (11B), 5/16" (21B), 3/8" (41B)
ASTM F883: Grade 4 (stainless steel shackle), Grade 6 corrosion resistance (Option E)
Options: Weather cover, custom stamp, corrosion resistance, key retained, non-key retained, chain options, OSHA lockout tags
American Locksets has stocked BEST B Series padlocks since 2001.
Trusted Since 2001
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