How tall is your box? Are you 90 or lower? Ever do one legged box squats?
I have 3 - 10" / 4 " / 3" that I can stack.
17" is the "high" box, which is about at the patella tendon on my leg and is supposed to be the parallel/slightly above. 14" for low. Use the 3" solo for RDL...etc...
I alternate the high / low. The weight difference is substantial between the two.