I heard from a sanitation man FLUFF is all the left over unusable mix of glass plastic foam etc from the metal industry from cars and other appliances after shredder .
So i used a spread sheet to keep track of how much non metal actually i might be including with my mix by estimating the weight of items i see are true metal . Metal items that could have foam plastic glass i now can see how much i might give per order
I can see how to lower the FLUFF in my mix and see really how if your not careful you can accidentally get paid for to much FLUFF
some yards are also more forgiving so i can balance out according to yards preference.