Quickly tried. The softbox is easy to assemble, the magnets snap the spacers into place and keep the structure of the softbox intact. When using it on the Neewer 660 LED with barn doors you can hang the softbox on the top barn door and it even works without straps to secure it. A small gap will remain on either side of the barn door, but that is not a problem. The opening of the softbox fits well with the size of the LED panel. So the 660 LED + Medium softbox will work just fine.