This tremolo control box can be used with many Hammond Organ models including A, B, C, D, E, BV, CV, B2, C2, RT2, B3, C3, RT3, A100, L100, and M100. It can be used with various Leslie Speaker models including: 122, 122R, 122RV, 222, 22H, 22R, 21H, and 31H (above serial number 5200). The control box has been rebuilt with new components (capacitor and resistors).