GEAROLL Spark Plug Gap Tool with 32 Blade Steel Feeler

GEAROLL's Spark Plug Gap Tool is a compact hand tool with a 32-blade steel feeler gauge that lets you set accurate spark plug gaps for most 10mm, 12mm, 14mm and 16mm threaded plugs quickly and reliably.

Whether you tune motorcycles, lawn mowers, cars or small engines, a correct spark plug gap helps the ignition system run as designed. The GEAROLL kit pairs a precision-feeler blade set (0.001"–0.040" / 0.03mm–1.0mm) with a threaded gapping head and a simple knob adjustment so you can size and set non-preset gap spark plugs without special equipment. The tool is black-finished for durability and arrives ready-to-use with protective gloves included.

How does this tool create a consistent spark plug gap?

The tool uses a screw-driven clamp to open the side electrode to the exact spacing indicated by the selected feeler blade. Insert the plug into the gapping head, rotate the knob to expand the electrode, then check with the feeler blade and fine-tune. Backing the screw slightly before measuring prevents false readings from electrode rebound.

• 32 hardened blades cover 0.001" to 0.040" (0.03mm–1.0mm) for precise measurement.
• Threaded gapping head accepts most 10mm, 12mm, 14mm and 16mm standard plugs.
• Knob-driven expansion gives controlled adjustment without hammering or prying.

Which spark plugs are compatible with the GEAROLL gapping tool?

This gapper fits the majority of standard-thread spark plugs found in small engines and many cars and bikes—specifically 10mm, 12mm, 14mm and 16mm threads. It is not designed for 18mm thread plugs or for extremely long-reach or very short-reach specialist plugs. Always check the plug thread and reach before using the tool.

• Compatible: standard 10mm, 12mm, 14mm, 16mm threaded spark plugs.
• Not compatible: 18mm thread, long-reach or short-reach specialty plugs.
• Works with non-preset gap plugs that require manual adjustment.

How do I use the included feeler gauge and avoid damaging the plug?

Choose the blade that matches the manufacturer's recommended gap, insert it to confirm thickness, then clamp the plug and adjust slowly. After reaching the target, slightly reverse the screw before re-checking with the blade to avoid electrode rebound affecting the measurement. Avoid forcing the clamp so plating or electrode coatings aren’t scraped.

• Select the correct blade; the set ranges from 0.03mm to 1.0mm for fine control.
• Turn the knob incrementally; never over-tighten or force the plug into contact.
• Rotate the knob back slightly before measuring to prevent false readings.

What comes in the kit and how durable is it?

The kit ships with the gapping tool, a 32-blade 65-manganese steel feeler gauge and a pair of gloves so you can start work immediately. The blades are hardened and polished to resist wear and give repeatable thickness. The tool’s finish and simple mechanical construction are built for garage use and field service.

• Included: 1 spark plug gap tool, 1 32-blade feeler gauge, 1 pair of gloves.
• Feeler blades: 65 manganese steel, hardened and polished for accuracy.
• Low-maintenance: simple screw mechanism and durable finish for long service life.

Who is this for: GEAROLL’s Spark Plug Gap Tool is aimed at DIY mechanics, motorcycle and small-engine enthusiasts, fleet maintenance staff and anyone who needs a reliable, portable way to set gaps on standard-thread spark plugs. It’s ideal if you want a repeatable, tool-based method that’s faster and less abrasive than bending electrodes by hand, but it’s not intended for rare 18mm or specialty plug types.