That's just bulk wire. High quality bulk wire can be found for very reasonable prices at places like Monoprice.com.
Also, if useing the whole length of 50' for one speaker wire, it is recommended to use a thicker gauge wire.
I run my 9 speaker system with 50' speaker lines, but mine are 10 gauge. Overkill I know, but better safe than sorry when they're routed though ceiling and walls.
Normally, I would recommend 12 gauge for longer runs, and 14 gaurge for shorter runs, but use the same gauge for all wires in the same system.
I never use 16 gauge. 16 is just too small to bother with when 14 is better and alreay cheap enough.