This rack panel is awesome, it fits exactly one HU and has holes in it so that air can circulate into and out of the rack. And the mounting holes are oblong so that even if you built four rack yourself (and did it poorly) this will probably still fit! Also, it is flat black, so it won't draw your eyes from the knob twiddling.
Watch it though, it does not come with screws, so you need to sort that out separately, and for this reason I deducted a star in the total.
Ok it's just a piece of metal that does exactly what it is supposed to to, sorry if the review went a bit far...