Part numbers:
41X1178

Common error codes:
920, 921, 922, 923 error = Fuser unit isn't at the right temperature.
121.24 error = Fuser never reached the fuser detection temperature.

Compatible models:
B2338dw, B2442dw, B2546dw, B2650dw
M1242, M1246, M3250, M3350
MB2338adw, MB2442adwe, MB2546adwe, MB2650adwe
MS321dn, MS421dn, MS421dw, MS521dn, MS531dw, MS621dn, MS622de, MS631dw, MS632dwe
MX321adn, MX321adw, MX421ade, MX521ade, MX521de, MX522adhe, MX532adwe, MX622ade, MX622adhe, MX632adwe
XM1242, XM1246, XM3250, XM3350