Cable Company told me about 3 choices for tail length. I runs 2 pair of 16 inches tails for biwiring.
One caution as it has been mention, Speaker Cells are quite light and with Apex speaker cables, they may not sit so easily on the floor. Also, my speaker terminals are about 12 inches off the floor so I thought that 16 inches tail would be enough. I was wrong. The tail are not very stiff but not exactly flexible either and 2 pairs of them with Apex speaker cables at the other end, I could not really find a way to have the speaker cells sit on the floor without putting extra weight on them. In the end, I have to get a 2 inches block to put under speaker cells so all spikes on the speaker cells can have solid contact with the floor.