Just to point out that any product is not fool proof (said he throwing a spanner in the NGK works) we buy plugs in boxes of 10, the last but one box we had, out of the 5 taken from the box the first 3 wouldn"t spark at all & the next 2 the saws fitted with them ran like crap, but had been OK before fitting & were OK with the old plug refitted, the box was returned to the supplier & we had to wait over 2 months for NGK to admit they were faulty & refund, the only 2 brands of spark plugs ( used over the last 35 years that has had zero problems were KLG ( no longer manufactured ) & Nippon Denso ( now in our area ) almost unobtainable. all other brands have had some sorts of problems. But looking at the bigger picture the more units produced the greater the % chance of failures, in this throw away world it"s a pay your money & take your pick ( as an aside posters on here really take swipes at Champion) no doubt with good reason, & yet we have had less problems with them, than with either NGK or Bosch, so it"s all a bit take it as you find it.