I have never used one, I do wrap the receiver in 1/2 foam rubber taped to hold the receiver secure and placed in a plastic bag, with the opening taped or tied shut. Then I either wedge the receiver in some secure location, or I use thread or cable ties to tie it somewhere to keep it from moving around. I guess I've always thought in a bad crash there is simply going to be the possibility of damage to the radio components and I will need to replace or repair those damaged components. I have a hard time justifying the added weight of the crash box and have some doubt as to its' ability to keep the receiver from being damaged, anyway. Now, this is my opinion, only. Obviously some of you think differently and I think this is exactly right!