(shipping included) => 5"x8" ($7.95/bracket), 8"x12" ($10.95/bracket), 12"x18" ($13.95/bracket), 15"x21" ($15.95/bracket), 18"x24" ($20.95/bracket), 24"x24" ($25.95/bracket), 24"x29" ($27.95/bracket).
At first glance, they might seem expensive, until you start pricing what's available at box-stores for "less heavy-duty" shelving, and see these brackets are sold as pairs with shipping included.
