goodo , depends on heat ranges too . if you like to burn a hole in something ? then allgood , or run rough , wrong reach (at best close the gap , worst damage a piston) never hurts to ask anyone anything
The C8J and RJ19LM are the same heat range of hot. The RJ19LM is resistor plug for RF noise suppression. In older engines that have borderline compression the C8J will give better performance as it will more spark energy at the tip. Both are 14mm with 3/8" reach.