Resistor	Shell Design	Heat Range	Firing End Design	Wide Gap Designation - if applicable
R	C	12	YC	4
R - Resistor	C - Thread size - 14mm, Reach - 3/4", Hex - 5/8"	12 14 - hotter than a 12	Y - Standard Projected Core Nose C - Copper Plus Design	Wide gaps required to meet Federal and California requirements. - 4 to 8.

Spark Plug #	Price	Purchase Now
RC12YC For Generac RV's 220 (older models), 360/410, 480/570. For Briggs & GE's Home Standby Generators - 7 - 20kW Generac Guardian 10 thru 15kW, and current model 20kW Generac Guardian Liquid Cooled - 1.6L HSB Chevy, 2.4 L HSB Hyundai	2 - RC12YC - $6.49
RC14YC	2 - RC14YC - $6.49
XC10YC - For 17/18/20kW RES and RESL Kohler	2 - XC10YC - $9.90