Allows efficient circulation of heat throughout entire heating area. Works with Item#s 177562, 177563, 177564, 177565, 177599, 177600, 177601, 177602, 177610, 177611, 177614, 177615, 177633, 177634, 177635, 177636, 177637, 177638, 177639, 177640, 177612, 177613, 177617, 177616, 177641, 177642, 177643, 177644 and 177920.