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Product Description
H-D #37-09A
USA made Champion 18mm thread SPARK PLUG Pair
with equivalent heat range of original #1 H-D plugs (hot)
Fits 1909 - 1947 Harley motors
Thread reach of these modern Spark Plugs is 1/2"
Original HD Air Cooled Plugs was 3/8"
You may want to use a set of our Aircraft Copper Spacers when installing these plugs in your Knuckle or Flathead motor

