At 5mm the base is fairly thin. Attached to it are 25 copper fins spaced apart 2.5mm. You'll also notice the copper rods that stretch from one end to the other. They do not connect to the shroud, but rather from the first fin to the last. It's too bad that Kingwin decided not to pack in more fins on this bad boy. By reducing the spacing to 1.5mm they could have fit in 40 fins instead of merely 25, which would undoubtedly help out performance quite a bit. 1.5mm spacing is hardly what you would call "microfins", but it would increase the overall surface area quite substantially.