If you worry about the opening the Micro Mecha-Box, please look at these pictures for information of maintenance and cutom.
And try to custom it!!

 
1.
MP7A1 Mecha-Box.
We start from here. 		2.
It could open(The part of Red sircle), so clip it. 		3.
The parts pop out from box by spring tension when open it. So put Cylinder from outside and take careful.
4.
Open the box.
And put Cylinder, Piston, Guide, Spring out.
 5.
Shift gears to the other side box for understanding the position of them. 		6.
Keep going...
Completion
7.
Keep going...		 8.
Finaly, close the box.
(Put the other side on)

It idn't easy for everyone.
But if you

understand the position of the parts inside box, you can make it easy.
Be careful with the release of the Spring tension.