ok so im going rack. and im getting soem sliding rack shelves. only problem is i dont know that the rack shelves will fit in the rack. the rack is 18 inches deep rail to rail. how will i know that my rack shelves fit? does the rack or rack gear come with teh proper mounting screws? what are the little white things in this photo that are holding the cables to the rack? in know a lot of it is zip ties but some of them are on those white things. and what is up with all those colored cables and and aluminum boxes. i dont have all that in my rack. am i missing something? i suppose thats it for now...thanks.