To increase the maximum stackable number of containing holders 13 while keeping manufacturing costs low, and work easy.

The bead B with filler F in the form of a flange is placed on a roughly flat placement part 15, where those of different diameter (inch size) can be placed without problems. The total number of the containing holders 13 required can thus be reduced. When the containing holders 13 are stacked, axial direction distance (vertical direction space) between the containing holders 13 vertically adjoining each other need only be a little larger than width of the bead B, thereby the maximum stackable number can be increased.