I've experimented with many materials for flagging. Some serious testing.
Here in the east we have lots of rain and added snow with freezing conditions.
Christmas tree tinsel, fur. feathers & fake fur gets wet or freezes and doesn't perform on a constant. daily basis.
Cardboard gets wet and fall apart. Tyvek when colored on one side fades. CD's are a bit bulky & break if one is not careful.
Thru my testing, I feel I found the ultimate flagging material. It's readily available in farming communities and FREE for the asking.
It's call AG BAGS. Ag bags are the long, white, tube like bags used to store feed. As farmer cuts off end of bag to get at feed, he discards these cut offs. He will give you all you want if you ask. When finished using all his Ag Bags, farmer has to pay to haul cut offs to landfill.
Ag Bag material is made to take the weather. I've tested it in all conditions, high winds, rain, snow, freezing rain, summer heat. It has not failed.
It never fades and is made to shed water. Plus it is white on one side and black on the other side. In which I feel is a perfect combination of flagging colors.
Ag Bag with cut offs laying around...
1 1/2" wide x 8" long seems to be the right size.
Thru testing in high winds, eyelet isn't necessary in this tough material.
Here I added eyelet for professional look, since I was making some for a friend.
A fishing snap swivel in needed to make the light weigh material spin & dance in a slight breeze.
*For folks that need a little flash or sparkle just add hot glue & sparkle