This is the glow plug typically used on our slightly older heaters before we switched to the glow plug with the blue plug and white wires. Make sure you order the right glow plug for your unit. 

It should be noted that we use high-quality glow plugs and they rarely, if ever, go bad. We almost never see cases in support where replacing the glow plug resolves issues our customers may be experiencing. Rather, it's typically issues with fuel lines/delivery.