OK, thanks, now we are getting somewhere, from what I am finding, the DENSO ZXU20HCR8 (Denso 3479) spark plug in your picture fits the Hyundai Accent and Veloster, the preset plug gap is 0.031"… The correct OEM spark plug is NGK SILKR7E9 (NGK 95229) and preset plug gap is 0.035"… Getting conflicting info about the correct plug gap, seeing 0.035" or 0.043"/0.044"…
I am only seeing O’Reilly auto parts and Napa auto parts carrying or the dealer carrying the spark plugs $20 each and up… AutoZone and Advance Auto are NOT showing to sell the NGK 95229…
eBay, Amazon and even heard of Rockauto having counterfeit NGK spark plugs, so stay away from places like that, stick with O’Reilly or Napa, or best is the dealer for the plugs and coils…
Now, in the pictures of the spark plug(s) the non threaded part looks very clean, did you wipe it down or clean it???