The kidney or spacer plate discs are something that should have come with our meat grinders from factory. If you try and grind your meat and then stuff sausages you'll end up with either double ground meat (too fine of a consistency) or seasoning which has not mixed thoroughly enough. Y These discs allow you too grind your meat and fat, add your seasoning and mix it by hand until desired flavor is achieved, replace with kidney/spacer disc and then run the same seasoned ground through your grinder a second time with no I'll effects. This eliminates the need for an addition sausage stuffer!! I would have given it 5/5 if the centre circle was smaller to allow more through but it's not a big deal. PS this fit perfectly in my Waring Pro Grinder!