Can you use this on back and leg day for back growth and leg growth

the hex bar is a logical choice. Instead of needing to use a mixed grip or pronated grip, you get something more natural. That is a neutral grip, to your sides, like you would use to lift two grocery bags.The hex bar may allow a heavier load to be lifted, because the external moment arm lengths at the hip, knee, and ankle are all shorter than with a straight bar.

@RilwanG A deadlift is not a back movement. However, you CAN still use a deadlift (hex bar, sumo, conventional, any variation) on your PULL day or on your LEG day. Either day or even both days would be OK. But again, it's not a movement to build your back. Your legs are going to get the most out of a deadlift because remember, you're technically pushing the ground away.