I’ve used Swiffer duster products for years; regular and heavy duty.  I purchased a new box last week and when I opened the box and tried to use the 360° heavy duty duster, the slots for the duster prongs are not aligned and the seam is to far offset.  I’ve check through the whole box and each duster is like this; improperly manufactured.  Even trying to use these on the duster arm results in one prong coming the other side of the duster and could potentially scratch surfaces if you didn’t realize soon enough what happened.