The feathers or down, used by themselves or mixed with other materials, are chosen primarily for their good thermal insulating characteristics.
(The feathers or down; used; by themselves) (The feathers or down, used by themselves or mixed with other materials; are chosen; primarily for their good thermal insulating characteristics)
The feathers or down The feathers or down, used by themselves or mixed with other materials
used are chosen
by themselves
primarily for their good thermal insulating characteristics