TM M4 S-Style Mechbox
 

I need to put a new mechbox in my TM M4 S-Style.
I was thinking of this A.C.M. Complete QD Version 2 Mechbox.
Will this just drop in and work? I am worried about the back of it, it looks a little longer that any other M4 mechbox. Below you will find a link to the mechbox.
Any help would be great!

thank you

http://www.torontoairsoft.com/ACM-Co...4s_p_1611.html