The CC tuba is about 16 feet long, slightly shorter than the BBb, and generally has a faster response and a clearer centered tone.  This is the standard instrument in American orchestras, and most players looking to attend a conservatory in the US will look to owning a CC tuba.  A CC tuba most often has 5 valves, which will allow low F, a commonly played note, to be right in tune.  Four valve CC tubas may require a bit of slide pulling.