Spectrum Chemical manufactures and distributes fine chemicals with quality you can count on including those with CAS number 51-21-8, Whether you call it Fluorouracil, 5-Fluorouracil , 5-Fluoropyrimidine-2 -4(1H -3H)-dione or 5-FU you can be assured the Fluorouracil products offered by Spectrum, meet or exceed the grade requirements or specifications for each individual product.