Naylor SR-13 Finnish Contraflow Masonry Heater & SR-18 Russian Bell heater. Finished with 4″ CMU and clay plaster and whimsical thin fieldstone veneer by Eric | May 30, 2014 | Contraflow Heater, Masonry Heater, Masonry heater core, Russian Bell Masonry Heater, SR-13 core, SR-18 core, Stucco heater, top vented masonry heater