SKU: 76145787795

HKS Super Fire Racing Spark Plug 50003-M525RE

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Description

HKS Super Fire Racing Spark Plug 50003-M525REM Series Super Fire Spark Plugs HKS M Series spark plugs are high performance Iridium plugs designed to provide improved ignition performance, durability and anti carbon build up. 0. 6mm Iridium Alloy Center Electrode Outer Electrode with Platinum Chip Short Type Outer Electrode (Anti Vibration) Thermal Edge Spark Support Gap M Series is recommended for reliable ignition, durability and anti carbon buildup under high load. The Iridium alloy is used

M-Series Super Fire Spark Plugs

HKS M-Series spark plugs are high performance Iridium plugs designed to provide improved ignition performance, durability and anti-carbon build-up.

  • 0.6mm Iridium Alloy Center Electrode
  • Outer Electrode with Platinum Chip
  • Short Type Outer Electrode (Anti-Vibration)
  • Thermal Edge
  • Spark Support Gap

M Series is recommended for reliable ignition, durability and anti-carbon buildup under high load.

The Iridium alloy is used because of its durability and reliability.  On an average plug, a narrow core typically shortens life span of plug but with the intense durability of iridium there is no sacrifice in any longevity.  With a high melting point of 2454 degrees C, opposed to the 1769 degrees C of white gold, the electrode can tolerate the high levels of compression and minor knocking without any deterioration. A nickel coating on the housing also prevents the spark plug from premature deterioration.  The Iridium plugs are available for multiple applications and offered in "colder" heat ranges of 7 and up and specifically for rotary, heat ranges of 9 and up are offered.

Heat Range: NGK # 10.5
Thread Size: 14mm × 12.7mm
Wrench Size: 20.8mm

Fits:

1983 - 1985 MAZDA RX-7 ALL ALL From 10/1983 Thru 9/1985 Production Date  SA22C Chassis  Stock Plug/Heat Range: ROTARY:9
1985 - 1988 MAZDA RX-7 R2 1.3 From 10/1985 Thru 8/1988 Production Date  FC3S/FC3C Chassis  Stock Plug/Heat Range: ROTARY:10,11
1988 - 1991 MAZDA RX-7 R2 1.3 From 9/1988 Thru 12/1991 Production Date  FC3S/FC3C Chassis  Stock Plug/Heat Range: ROTARY:7,9
1993 - 1995 MAZDA RX-7 R2 1.3 From 12/1991 Thru 8/2002 Production Date  FD3S Chassis  Stock Plug/Heat Range: ROTARY:7,9
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Exchange/Return Notes
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SKU: 76145787795

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ChelaTho813
Omaha, US
★★★★★ 5
The only one I'll use!
As the title says, this is the brand to get!! It's fast-acting, doesn't give me weird dreams like some do, and I never wake up feeling groggy.
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Reviewed in the United States on March 13, 2025
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Belle of the Ball
Omaha, US
★★★★★ 5
Works wonders
I've been buying these for well over a year now as Subscribe and Save. I work 12 hour overnights as a nurse. My sleep schedule normally gets messed up. I would have no problem falling asleep but would wake up only a few hours later which is not good when you have work again that night. We buy these on Amazon due to the great price and the fact that they are extended release which helps keep me asleep longer. When I take 1 or 2 of them, I am able to sleep about 7-8 hours which is great. I take this both when I sleep during the day and sleep during the night. It helps me sleep no matter when and I am able to adjust my sleep schedule often. I have recommended them to many.
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Reviewed in the United States on January 10, 2013
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Verified Purchase
PSBone
Carnegie, US
★★★★★ 4
Works quite well, dose still a bit high for me
Used to take the Natrol 5mg slow release, now that I can compare these 2, I love this more. It doesn't make me feel too edgy, it's quite relaxing actually. I still have to halve the dose as the full dose makes me groggy the next day. Where the Natrol gave me very vivid, but not unpleasant dreams, these don't make me dream as vividly. It does take a bit longer to get me to sleep, but once asleep, your asleep. Highly recommend, once I finish this bottle, I'd get the 2mg tr next time, as a lower dose works better for me.
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Reviewed in the United States on July 10, 2014
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Eudy Ernesto De León Batista
Fort Morgan, US
★★★★★ 5
Excelente Muy Satisfecho
Servicio excepcional, cuidadoso, el producto muy bien empacado. Y el tiempo de entrega fue el acordado. Y del producto ni hablar, excelente.
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Reviewed in the United States on February 3, 2026
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Dog Mom
Natrona Heights, US
★★★★★ 5
seems to work just fine
Helps me sleep. I also use Mg, B complex and medical cannabis oil before bed. My sleep isn't great otherwise here in the good ol' USA (unlike in Europe where I sometimes go for complicated issues/not vacation; which indicates issues with the much higher radiofrequency exposure allowed in the US than in the European country where I sleep like a happy baby). Just wait for 5G, then I probably need to reinvent my sleep protocol if I want to get any rest. But well, with the 5G impact on the biosphere, we may not be here much longer then. That means we better stop 5G before it's all roleld out.
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Reviewed in the United States on August 2, 2019

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