★★★★★
GOOD PRODUCT
Michael Y.—February 20, 2026✓ Verified purchase
VALUE WAS GREAT FOR QUALITY. FIT WAS PERFECT START WAS RIGHT ON. POWER WAS IMPROVED. DURABLE AS IT SHOULD BE Read more
NGK
NGK CR9EIX - Iridium IX Spark Plug - 4-Pack -
$35.99$59.99
About this item
- 4 pack NGK Iridium IX 3521 Spark Plug
- Genuine NGK Parts
- Includes original packaging and hardware
- Direct replacement auto parts
- Confirm vehicle fitment with Amazon Confirmed Fit
$35.99
Was $59.99Save $24.00
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Product details
| Brand | NGK |
|---|---|
| Core Material | Iridium |
| Thread Size | 10mm |
| Top Material Type | Iridium |
| Vehicle Service Type | Car, Truck |
Technical specifications
| brand | NGK |
|---|---|
| core_material | Iridium |
| thread_size | 10mm |
| top_material_type | Iridium |
| vehicle_service_type | Car, Truck |
| automotive_fit_type | Vehicle Specific Fit |
| oem_part_number | 7085731 |
| manufacturer | NGK |
| model | 4 pack NGK Iridium IX 3521 Spark Plug |
| item_weight | 4.5 ounces |
| product_dimensions | 3.31 x 0.94 x 3.32 inches |
| item_model_number | 3521 |
| is_discontinued_by_manufacturer | No |
| manufacturer_part_number | CR9EIX |
| position | Front, Rear |
| best_sellers_rank | #12,033 in Automotive ( See Top 100 in Automotive ) #57 in Automotive Replacement Spark Plugs |
| date_first_available | April 10, 2012 |
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Customer reviews
4.8495 ratings
- 5★88%
- 4★13%
- 3★0%
- 2★0%
- 1★0%
Customers say
Customers find these spark plugs to be of good quality, with one mentioning they're the best plugs for the M8 Harley. Customers like the throttle response, with one mentioning improved performance at both idle and full throttle.
★★★★★
Good
Dianne S.—December 2, 2025✓ Verified purchase
Great price for these quality spark plugs. My bike is running better! Read more
★★★★★
Great plugs
Bill—October 15, 2025✓ Verified purchase
I installed these in my 2021 Indian Scout Bobber ABS. I can see the improvement over the regular plugs. The bike starts better and runs better at idle and full throttle. I recommend them. Read more
★★★★★
Great product, great price, great company
Jae—December 1, 2025✓ Verified purchase
Great!! Can’t go wrong! Read more
★★★★★
Dealer performance without the dealer price
CmfmotorSports—March 10, 2026✓ Verified purchase
NGK CR9EIX Iridium IX Spark Plug – 4 Pack Installed these in my bike and it fired right up with no skips or hesitation. These appear to be very comparable to the much more expensive Screamin’ Eagle plugs sold by Harley. Looking at them side by side, they seem to be essentially the same plug with different branding. They come with a preset gap, which is a nice plus. Of course my OCD still requires me to check them anyway, but all four were spot on and didn’t need any adjustment. I can’t speak yet to long-term durability, but NGK has a strong reputation and I expect them to hold up well. For reference, these were installed in a 2019 Harley-Davidson Softail 114. Overall, a great value compared to the dealer-branded option. Read more
★★★★★
Muy buena calidad, lo recomiendo
Raidel—March 14, 2026✓ Verified purchase
Muy bueno el producto lo recomiendo Read more
★★★★★
Harley Plugs
Bubba Byars—February 3, 2026✓ Verified purchase
Bike seems to idle & run better Read more
★★★★☆
As described
44sal—August 23, 2025✓ Verified purchase
As advertised Read more
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