A freewheel and a cassette are no the same thing. A cassette is a set of cogs that slides onto the splines of a freehub while a freewheel screws onto a threaded hub. I'm guessing that you are talking about a freewheel since you are here in C&V. If so, IRD freewheels are nice quality and come in a variety of cog counts Classica Freewheels 5/6/7-Speed ? Interloc Racing Design / IRD. There are also a few Shimano and Sunrace freewheels but the cog count is very limited.