3AG is the size form factor: https://electronics.stackexchange.com/questions/61297/what-does-3ag-mean-in-fuse-block-3ag Most popular such fuses in the USA are Littelfuse and Bussman. Here's a Bussman cross-reference: http://www.cooperindustries.com/con...t-literature/bus-ele-pp-10006-fuse-finder.pdf Littlefuse info: http://www.littelfuse.com/products/fuses/cartridge-fuses/3ab_3ag-6_3x32mm-fuses.aspx Don't buy cheap, no-name/no-brand fuses. Sooner or later, you'll regret it. And the results won't be pretty. Mouser Electronics is your friend. Unless an extraordinary emergency, never substitute a higher value or use slow-blow when fast/normal blow are specified. Know that if you do, a fault in your electronic equipment could fry circuitry and faithfully protect the fuse -- the exact opposite of what is supposed to happen. Think "weak link."