Suburban Furnace Model NT-20SE Tune-Up Kit comes in two variations. The first (Kit #1) has a single sense electrode (one wire that goes to the electrode), the second (Kit #2) has a dual sense electrode (two wires that go to the electrode). Please verify which kit is applicable to your furnace prior to ordering.
Tune-Up Kit #1 Contents (links):
Tune-Up Kit #2 Contents (links):