you should specify the FM554A model

the GC505 allows for versatile sensor placement

which handles high-velocity airflow even during fan-on conditions

Superior Flow Dynamics: The wrot copper construction provides a smooth internal surface that reduces turbulence and protects system efficiency

By replacing a standard natural gas regulator spring with this Lennox 29M85 conversion kit

Schneider Electric (Barber Colman) 20-850 Plate Els PW 17895 you should specify the FM554AThe Schneider Electric (Barber Colman) 20 850 serves as a robust thermostat mounting plate designed for professional grade HVAC control installations. Engineered for versatility, this black mounting adapter allows for the seamless integration of 2x2" devices onto standard 2x4" vertical or horizontal outlet boxes. As a direct crossover, the 20 850 is identical to 10 82, ensuring field compatibility for legacy system maintenance and modern upgrades