That would be Cat5E <-- Enhanced Cat5 can do up to 300MHz vs 100MHz for Cat5. 
It can be used for GigE, but the range is pretty short, about 1/3 the length
that you could do 100Mb Ethernet.

> > Cat 5 cable is what you use to make ethernet cables.  Cat 5 supports
> > standard ethernet (10Mbits/sec transfer rate) and fast ethernet
> > (100Mbits/sec transfer rate).
> 
> Isn't it also used for gigabit networking?