I'm definitely not an expert but his purely optionial. I'm lucky because my machine has two ways to FMQ; with one foot like this one it does hop up and down and the other one doesn't; it hovers over the fabric. When it hops up and down it'll actually be holding the fabric down during the stitch; the other one does not. The viking rep says this is better than using the floating one. I've had others who prefer the floating on to the hopping one (not sure the accuate name) but it's built into my machine so I don't have to worry what its called; I just click on the icon and it shows me the two options and I chose one and make sure the correct foot is installed.