You need to think of items like you would food, or dog food even.. every dog food label doesn't "make their own" food.. they goto a factory that MAKES DOGFOOD.. somebody walks in and says "hi, I wanna make my own dog food label", and here's the recipe I want.. Manufacturer responds "ok, well here's the list of all the ingredients we've sourced and can get bulk supplies of, let's sit down and see how close we can get to what you want using our stuff".
Same thing with tool boxes and stuff.. they'll offer 3 different gauges of steel, 3 different slide options, 8 different colors.. and they pick from it like a menu.. certain "recipes" are probably reserved for certain buyers or brands - and that's why you'll see 20 different screwdriver companies selling the same screwdrivers basically. But they have different shaped handles, different color grips, different grade metal.. they create their own combination to launch their own brands, all from the same manufacturing facility.. did you think shoprite had their own factory for every "shoprite brand" item they have in the store? No - they approach 40 different manufacturers that can each make a different food item, and package it in a box that says "shoprite" on it, all with their own slightly different recipe.