A plugs hex size determines the socket required for installation.

While 5/8" (16mm) and 13/16" are the two most common plug hex sizes, plugs can have a hex as small as 8mm or larger than 1".

If you're a tuner or engine builder in search of the perfect spark plug for your current project, pay special attention to the hex size required. Remember to take into consideration not only the diameter of the cylinder head, but also the added thickness of the plug socket needed for installation.
A spark plugs threads are comprised of 3 dimensions: Reach, Diameter and Pitch.
A spark plugs reach is calculated by the length of the threads. It is measured from the seat of the plug to the end of the threads.

It should be noted that the reach does not include the electrodes, or an extended metal shell. When custom-selecting a spark plug, the electrode length and projection should be included in the calculation when taking into consideration the clearance in the combustion chamber.

Please use our vehicle lookup to find the correct OE type plug for your vehicle.

Use of an improper plug in an engine will result in engine damage.
A spark plugs seat creates a seal to the combustion chamber.

There are two seat types available: flat and tapered.

WARNING: Spark plugs with different seat types are NOT interchangeable.
*Spark plugs with a flat seat must be used in engines designed for a gasket seal.
*Spark plugs with a tapered seat must be used in engines designed for a tapered seal.

SELECT YOUR VEHICLE:

PRODUCT CATEGORY:

Nitrode™ Performance Products
Nitrode™ Lawn & Garden

Product Features:

  • The Nitrode™ is made with a proprietary ceramic exclusively used for this spark plug.
  • This unique ceramic is over 10% harder than any ceramic know today!
  • Harder ceramic offers many advantages, one of which is making this the best antifouling plug available.
  • Copper core center electrode.
  • Yttrium neutral electrode.
  • Premium resistor.
  • Triple chrome plated.

Product Catalog:

CatalogDownload Product Catalog for detail application information

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Nitrode™ Performance Spark Plug
Part #: SP-NP28

Specification:

  • Hex: 20.8 mm
  • Thread: M14x1.25 mm
  • Reach: 9.5 mm
  • Resistor: Yes
  • Seat Style: Gasket Seat
  • Center Electrode: Nitrode Bridge with Yttrium
  • UPC: 757558045358
  • Packaged Dimension: 3.5"(H) x 1"(W) x 1"(L)
  • Packaged Weight: 0.055 lbs
SP-NP28
SP-NP28
SP-NP28

Inquire info.   Where to Buy

 

Nitrode™ Performance Spark Plugs:

SP-NP20
SP-NP20C
SP-NP21
SP-NP21C
SP-NP22
SP-NP22C
SP-NP23
SP-NP24
SP-NP25
SP-NP26
SP-NP27
SP-NP28
SP-NP29
SP-NP30

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Amazon
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NUtrend
Summitracing
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