This is a chain designed to operate in two planes. It's an excellent Conveyor Chain which has many uses in a multitude of industries. DF-3500 Double Flex chain articulates on two planes with a large sliding area to decrease wear on chain and sliding surface and provides maximum flexibility for both horizontal and vertical movement. DF-3500 and DF-3910 have induction hardened inner link plates and cup-shaped outer link plates. DF-3498 has straight outer link plates for greater flexibility.