This is the Replacement Bulb that fits the following Fluorescent models: 503, 507, 520, 550, 563, 651, 676, 677, 821, 825, 826, 827, 904, 907, 920C, 935, 936, 964 & 8907.
Product Features:- Fits models: 503, 507, 520, 550, 563, 651, 676, 677, 821, 825, 826, 827, 904, 907, 920C, 935, 936, 964 & 8907.