Actually the red-brownish hairs mostly aren't fillers. They naturally occur in Asian hair in general. It depend a bit on the genetics, and some hair has more than others. Indian hair has some more than other Asian countries.

The reddish fiber are difficult to take color. While you might expect manufacturers to take them out, removing some of the hair mean throwing them away and losing some money.

They mostly get through the burn test just fine.

Suggestion:

- Wash the hair, see whether the hair get frizzy (frizzy = processed hair)

- Use a knife to scrape the surface of the hair until you get some powder. If the powder is white, it's uncolored. If it is yellow/brownish, it indicate precoloring (often done in processed hair to hide that the hair is from many donor.

- Bleach the hair to 613.

After that, you can be quite sure whether you really receive the virgin hair or not.