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PROTO Socket: Metric, 3/4 in Drive Size, 21 mm Socket Size, 12-Point, Std, Satin - 3/4" Drive Hand Sockets
PROTO3/4" Drive Hand Sockets

PROTO Socket: Metric, 3/4 in Drive Size, 21 mm Socket Size, 12-Point, Std, Satin

The PROTO Socket: Metric (MPN J5521M) is a 3/4" Drive Hand Socket with a 21 mm socket size and 12-point configuration. It features a satin finish and is not tether capable. This standard-length socket is manufactured…

SKU 3G-OTH-315093

Brand
PROTO
Item
Socket: Metric, 3/4 in Drive Size, 21 mm Socket Size, 12-Point, Std, Satin
Category
3/4" Drive Hand Sockets
Available to Order
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Local availability & support

Delivery
Worldwide DHL shipping from Singapore; 7–14 business days door-to-door for most destinations.
Payment
Invoicing in USD. Bank transfer (SWIFT) and corporate PO accepted.

Technical Specifications

PROTO
Manufacturer Part Number
J5521M
Type
12-Point, Std, Satin, Not Tether Capable
Socket Size
21 mm
Drive Size
3/4 in

Technical Documents

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PROTO Products
3G Electric (S) Pte. Ltd. — Singapore

Product Description

The PROTO Socket: Metric (MPN J5521M) is a 3/4" Drive Hand Socket with a 21 mm socket size and 12-point configuration. It features a satin finish and is not tether capable. This standard-length socket is manufactured by PROTO.

Frequently Asked Questions

What is the PROTO J5521M socket used for?

The PROTO J5521M is a 3/4 in drive, 21 mm, 12-point standard socket used for fastening and loosening metric hex fasteners in heavy equipment maintenance, industrial machinery assembly, and automotive repair. Its satin finish provides corrosion resistance.

What are the specifications of the PROTO J5521M socket?

The PROTO J5521M is a 3/4 in drive, 21 mm socket with a 12-point configuration, standard length, and satin finish. It is not tether capable. The manufacturer part number is J5521M. PROTO is the brand.

Where to buy the PROTO J5521M socket worldwide?

3G Electric supplies the PROTO J5521M socket to customers worldwide. We handle full logistics, customs clearance, and delivery to your site. Contact us for a quote and lead time. We source genuine PROTO industrial tools for global procurement.

How to select the correct PROTO socket for a 21 mm fastener?

For a 21 mm hex fastener, select a 21 mm socket like the PROTO J5521M. Ensure the drive size (3/4 in) matches your ratchet or torque wrench. A 12-point design offers more engagement angles than a 6-point, useful for tight spaces.

Used in

Common applications for PROTO
Automotive assembly — PROTO J72102 impact socket set for fastening lug nuts on production lines
Heavy equipment maintenance — PROTO J3772T flare nut wrench for hydraulic line fittings on excavators
General industrial repair — PROTO J795SA adjustable wrench set for tightening bolts on conveyor systems
Aerospace manufacturing — PROTO J5240A slotted bit socket for adjusting fasteners in confined spaces
Oil and gas pipeline work — PROTO J5438 12-point socket for valve assembly in refineries
Construction site toolkits — PROTO J8179-T500 double box wrench for structural steel bolting

PROTO Products

3G Electric supplies PROTO 3/4" drive hand sockets. We supply genuine products with in-stock availability on common SKUs, technical documentation, commissioning support, and warranty service — worldwide.

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Compatible alternatives & equivalents

Cross-referenced by specification & description
PROTO Socket: Metric, 3/4 in Drive Size, 24 mm Socket Size, 12-Point, Std, Satin, Not Tether Capable (MPN J5524M)
PROTO
PROTO Socket: Metric, 3/4 in Drive Size, 24 mm Socket Size, 12-Point, Std, Satin, Not Tether Capable (MPN J5524M)
PROTO Socket: Metric, 3/4 in Drive Size, 23 mm Socket Size, 12-Point, Std, Satin, Not Tether Capable (MPN J5523M)
PROTO
PROTO Socket: Metric, 3/4 in Drive Size, 23 mm Socket Size, 12-Point, Std, Satin, Not Tether Capable (MPN J5523M)
PROTO Socket: Metric, 3/4 in Drive Size, 27 mm Socket Size, 12-Point, Std, Satin, Not Tether Capable (MPN J5527M)
PROTO
PROTO Socket: Metric, 3/4 in Drive Size, 27 mm Socket Size, 12-Point, Std, Satin, Not Tether Capable (MPN J5527M)
PROTO Socket: Metric, 3/4 in Drive Size, 25 mm Socket Size, 12-Point, Std, Satin, Not Tether Capable (MPN J5525M)
PROTO
PROTO Socket: Metric, 3/4 in Drive Size, 25 mm Socket Size, 12-Point, Std, Satin, Not Tether Capable (MPN J5525M)
PROTO Socket: Metric, 3/4 in Drive Size, 41 mm Socket Size, 12-Point, Std, Satin, Not Tether Capable (MPN J5541M)
PROTO
PROTO Socket: Metric, 3/4 in Drive Size, 41 mm Socket Size, 12-Point, Std, Satin, Not Tether Capable (MPN J5541M)
PROTO Socket: Metric, 3/4 in Drive Size, 30 mm Socket Size, 12-Point, Std, Satin, Not Tether Capable (MPN J5530M)
PROTO
PROTO Socket: Metric, 3/4 in Drive Size, 30 mm Socket Size, 12-Point, Std, Satin, Not Tether Capable (MPN J5530M)

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PROTO Socket: SAE, 3/4 in Drive Size, 1 1/8 in Socket Size, 6-Point, Deep, Satin, Not Tether Capable (MPN J5536HL)
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PROTO Socket: SAE, 3/4 in Drive Size, 1 1/2 in Socket Size, 6-Point, Deep, Satin, Not Tether Capable (MPN J5548HL)
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PROTO Socket: SAE, 3/4 in Drive Size, 1 1/2 in Socket Size, 6-Point, Deep, Satin, Not Tether Capable (MPN J5548HL)
PROTO Socket: Metric, 3/4 in Drive Size, 46 mm Socket Size, 12-Point, Std, Satin, Not Tether Capable (MPN J5546M)
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PROTO Socket: Metric, 3/4 in Drive Size, 46 mm Socket Size, 12-Point, Std, Satin, Not Tether Capable (MPN J5546M)
PROTO Socket: SAE, 3/4 in Drive Size, 1 in Socket Size, 12-Point, Std, Satin, Not Tether Capable (MPN J5532)
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PROTO Socket: SAE, 3/4 in Drive Size, 1 in Socket Size, 12-Point, Std, Satin, Not Tether Capable (MPN J5532)