Spark Plug Socket 13/16″ (21 mm) 3/8″ Drive | KT Pro Tools

Description

Spark Plug Socket 13/16″ (21 mm) 3/8″ Drive | KT Pro Tools

Can’t get your spark plugs out? A proper spark plug socket makes the difference between a clean pull and a cracked insulator. This 13/16″ (21mm) 6-point socket is the correct size for the NGK BR8ES and D7EA spark plugs used across the Honda CB350, CB360, and CB450 family — and it works on every vintage Honda we support.

Why You Need This

Spark plug removal and installation is one of the most frequent maintenance tasks on a vintage Honda. If you’re using a regular deep socket or an ill-fitting plug wrench, you risk cracking the ceramic insulator or rounding the hex. A dedicated spark plug socket has an internal rubber sleeve that grips and protects the plug’s ceramic — and holds the plug in the socket so you can install it without dropping it into the cylinder well.

The 13/16″ (21mm) hex is the standard drive size for most spark plugs. This KT Pro socket also has an external hex on the end, so in tight-clearance situations where a ratchet won’t fit, you can grab it with a wrench.

Features

• 13/16″ (21 mm) 6-point internal hex
• 3/8″ drive — works with any 3/8″ ratchet, breaker bar, or extension
• Internal rubber sleeve protects spark plug ceramic insulator
• Rubber insert holds plug in socket for deep-reach installation
• External 21mm hex for wrench use in tight spaces
• Professional quality — KT Pro Tools lifetime warranty

Specifications

Note: Some models (CT90, CB175, CB200, CB500K, CB550, CB750) may benefit from our 18mm Thin Wall Spark Plug Socket in tight-clearance situations where the cylinder head recess is narrow.

About KT Pro Tools

KT Pro (King Tony) is one of the largest global hand tool manufacturers, producing professional-quality tools in Taiwan. All KT Pro tools carry a lifetime warranty. See our KT Pro Tools warranty process.

Frequently Asked Questions

What size spark plug socket do I need for my CB350?

13/16″ (21mm) — this socket. It fits the NGK BR8ES spark plug used on all CB350, CL350, CB360, CL360, CB450, CL450, and CB500T models.

Will this work on a CB550 or CB750?

The 21mm hex fits the plug, but the CB550 and CB750 have narrow cylinder head recesses. If a standard-wall socket won’t fit, use our 18mm thin wall socket instead.

What’s the difference between this and a regular deep socket?

A spark plug socket has a rubber insert inside that grips the ceramic insulator and protects it from cracking. A regular socket can crack the insulator on removal and won’t hold the plug for installation.

Does KT Pro have a lifetime warranty?

Yes. All KT Pro tools carry a lifetime warranty against manufacturing defects. See our KB article for the warranty process.

You Might Also Need

• NGK BR8ES Spark Plug — CB350 / CB360 / CB450 — the plug this socket is designed for
• 3/8″ Drive Ratchet Handle — KT Pro Tools — pairs with this socket
• 3/8″ Drive Ratchet Extensions — KT Pro Tools — for deep-reach applications
• Spark Plug Socket 18mm (Thin Wall) — for CT90, CB175, CB500K, CB550, CB750
• JIS Screwdriver Set (3-Piece) — another essential for working on vintage Hondas

Last updated: March 2026