Couldn't tell you what the "official" designation of the conduit is, but a quick check with a tape measure just now yields an OD of about 7/8", so it's probably 3/4" conduit, and the holes in the brackets have room left for a bit larger diameter. Each rack has 3 brackets, one at each end and one in the middle, spaced 6' apart in the long one and 4' apart in the shorter one. No sign of sag with a full rack of tires in either one. It's a 14' trailer, and with what I've seen with the two in there now, I wouldn't hesitate to go a full 14' with three brackets.