The Ko-ken 1/2″ Drive 5 Piece Extension Bar Set (KOPK4760/5) is a professional-grade socket extension kit designed to provide precise reach and improved access in tight or recessed fastening applications.

Manufactured in Japan, this extension set is engineered for mechanics, industrial technicians, and heavy-duty trade environments where strength, accuracy, and reliability matter.

This set includes five extension lengths ranging from 50mm to 250mm, giving you full flexibility across a wide range of workshop and field applications.

Why Use Socket Extension Bars?

In real workshop conditions, fasteners are often located:

• deep inside engine bays
• behind brackets or structural components
• inside machinery housings
• in hard-to-reach recessed areas

This extension set allows you to:

• access difficult fasteners without disassembly
• maintain straight-line torque transfer
• reduce strain and awkward tool positioning
• improve speed and efficiency in workshop work

Key Features

• 5-piece professional extension bar set
• 1/2″ square drive – compatible with heavy-duty sockets and ratchets
• Precision-machined Ko-ken Japanese construction
• Full range of common working lengths (50–250mm)
• Strong chrome finish for corrosion resistance
• Tight tolerance fit reduces wobble and play
• Suitable for high-load workshop applications

Included Sizes

This set includes the following extension lengths:

• 50mm extension bar
• 75mm extension bar
• 125mm extension bar
• 150mm extension bar
• 250mm extension bar

 Covers short access work through to deep recessed fastening jobs.

Applications

This extension set is commonly used in:

• automotive repair and servicing
• diesel and heavy vehicle workshops
• industrial maintenance and shutdown work
• mining equipment servicing
• agricultural machinery repair
• construction equipment maintenance

Why Ko-ken Extensions Are Different

Ko-ken extension bars are known for:

• extremely tight manufacturing tolerances
• reduced flex and improved torque transfer
• durable chrome vanadium steel construction
• smooth socket engagement with minimal slop

Compared to generic extension bars, Ko-ken tools deliver:

• better feel under load
• improved fastener control
• longer service life in trade environments

Straight Extension vs Wobble (Important)

This is a straight extension set, meaning:

• designed for direct torque transfer
• no intentional angular flex
• ideal for controlled tightening and loosening

For angled or offset access, a wobble extension set is more suitable.

Product Specifications

• Product code: KOPK4760/5
• Drive size: 1/2″ square drive
• Pieces: 5
• Lengths: 50mm, 75mm, 125mm, 150mm, 250mm
• Type: Straight extension bar set
• Material: High-strength alloy steel
• Finish: Chrome plated
• Origin: Japan

Who This Set Is For

Ideal for:

• professional mechanics
• diesel technicians
• industrial maintenance fitters
• workshop tool kits
• trades requiring reliable deep access tooling