The 3098-134 and 3098-156 mercury flame sensors are designed as universal replacements for types currently used on cycling pilot ignition systems. they will replace sensors used in thermocouple type (slip-in) pilot burners. the bulbs on both flame sensors have additional grooves to accept retaining clips (C-rings) allowing them to replace most existing sensors. the 3098 flame sensors are SPDT (single-pole double throw) devices, with switch cases designed to plug into cycling pilot gas valves. these flame sensors should not be used in appliances other than those listed in the cross reference.