Socket for spark plugs Honiton H4021, 1/2" drive, 21×65 mm

Honiton H4021 is a 21×65 mm spark plug socket with a 1/2" square drive designed to remove and install spark plugs in gasoline engines. The socket's extended 65 mm length allows access to recessed spark plugs, while the close-tolerance internal profile ensures secure engagement with plug hexes to reduce rounding and slipping. Constructed for workshop and professional use, this tool is suitable for routine maintenance and repair tasks on cars and light vehicles.

Advantages

The Honiton 21×65 mm spark plug socket provides accurate fitment to standard 21 mm plug hexes and sufficient reach for many recessed installations. Its 1/2" drive interface is compatible with common ratchets, torque wrenches and extension bars, enabling controlled tightening and loosening. The longer sleeve helps protect the spark plug during removal by guiding it straight from the well, and the secure internal profile reduces the risk of damage to the plug body.

Suitable for

• Removing and installing spark plugs on petrol engines with 21 mm hex plugs
• Automotive maintenance and service work in home garages and professional workshops
• Use with 1/2" drive ratchets, breakers or torque wrenches and extension bars

When it may not be suitable

This socket is intended for spark plugs with a 21 mm hex and may not fit plugs with different hex sizes or non-standard shapes. It is sized and shaped for gasoline engine spark plugs rather than diesel glow plugs or specialized ignition system components. For extremely tight or corroded plugs, additional penetrating lubricant or impact tools may be necessary and extra care should be taken to avoid thread damage.

Key specifications

• Socket size: 21 mm hex
• Overall usable length: 65 mm
• Drive size: 1/2" square drive
• Application: spark plug removal and installation for petrol engines

How to use

Select the correct 21 mm spark plug socket and attach it to a compatible 1/2" drive ratchet or torque wrench, using an extension if necessary to reach recessed plugs. Before loosening, clean around the spark plug well to prevent debris entering the cylinder. Fit the socket squarely onto the plug hex and turn counterclockwise to loosen. When installing a new plug, thread by hand initially to avoid cross-threading, then use the torque wrench to tighten to the manufacturer's specified torque value.

What to consider before purchase

• Verify your spark plug hex size is 21 mm to ensure compatibility
• Confirm that a 65 mm socket length is sufficient to reach recessed plugs in your vehicle
• Ensure you have a 1/2" drive ratchet or compatible tool for use with this socket

Usage recommendations

Use with a torque wrench for installation to achieve the correct tightening specification, and keep the socket and extension clean to prevent debris from entering the spark plug well. For seized or corroded plugs, apply penetrating oil and allow time to work before applying force.