tell them that unless they are comfortable with sending them then that is their choice but i strongly advise them not to do it especially if it is someone they don't know is asking for them. Many things could go wrong and they could end up regretting their decision so unless it is someone they have been with for a VERY long time and if they are comfortable with it then that is there choice.
Explanation:
I am NOT promoting anyone to send n*des what so ever just saying that it is their choice if they do
If the display case is cubic in shape and one edge is 15 inches then the other two edges will also be 15 inches each and since volume is lengthxwidthx height then the volume will be 15 x15 x 15 = 3375 cubic inches.