I have a rather eclectic collection of kitchen knives,including several 'Santoku' shaped ones, which is a real pain/impossible to try to find an (empty) knife block for. This product is great, as it doesn't matter if you have lots of knives of varying lengths and widths. I could have done with the dimensions of the block before buying it though, so I thought I'd include it for anyone else considering one.
Base - 9 x 5 inches
Height - 10 inches
Rods (ie space for knives) - 4 x 3.5 inches (this is the black area on the photograph)
All in all a great purchase - I am well happy with it.
One word of caution though....when you do come to washing the rods/insert, make sure it is completely dry before using it again as there is the possibility of rust forming on the knives otherwise. It is very difficult for the water to evaporate from the middle and base of the insert. I would advise wedging a few drinking straws down into the insert and leaving it out of the block for a couple days (change the positions of the drinking straws every so often so a different bit gets aired)