I got hold of a set while in, but did not like them for a couple of reasons.
They are just thin foam and don't provide protection from that comfortable firing range gravel.
Because they are inserted into the ACU's the pads like to drift and not stay where they are needed making you hesitant to drop in the prone not knowing what to expect.
ACU's are generally low quality stitching and material, so using them to scrape the cement/asphalt/Gravel will lead to a one day shelf life, in the military as you won't be able to use them afterwards outside of field duty.
So cough up an other $50's Private!
It's not like you are paid below the poverty line...