Nitterhouse quality concrete car and truck parking blocks are machine-cast with 5,500 psi, steel-reinforced concrete. The end result is a product that is smooth on the surface, yet extremely strong and very durable. Available in 6 ft., 7 ft., and 8 ft. lengths, these parking blocks are flexible enough to fit a variety of parking lot contours, yet rigid enough to withstand repeated abuse from cars and trucks.