1) Wefts: The first question that arises is that whether the weft is the single stitch or double stitch? The double stitch wefts reduce shedding and in that way they are much better.
2) Weight: The standard weight of sew-in hair bundles are 100 grams or about 3.5 oz. Sometimes to lower the rate wholesaler reduces the weight so always check "Is the bundle cheaper because it weighs less?"
3) 100% Human Hair: Not everyone wants 100% human hair, some want extensions only for the trendy look once. If you are looking for really cheap hair only a couple of times then consider a synthetic blend.
4) Remy or Non-Remy: Look that whether the hair is Remy or Non-Remy if you want tangle free hair always go for cuticle aligned Remy's hair.
5) Single Donor or Multiple: Single Donor hair is best. Before buying look that if the extensions are from the single donor or multiple. Single donor hair is best as hair is only from one person and the quality throughout the bundle is same and one feels like own hair.
6) Single or Double Drawn: I have discussed the difference between the single and double drawn in my previous blog. https://www.prarvihair.com/blogs/hair-beauty-health/double-drawn-versus-single-drawn. Most all human hair sold in the USA market is single drawn hair. The cost to produce a double drawn bundle is much higher because of the process of removing the shorter hairs is much expensive during the manufacturing process. Expect to pay more for a bundle of human hair that has long hairs all the way to the tips.
7) Colored or bleached: The key question again that arises is that "Can you color or bleach the hair?" The best quality virgin hair will lift all the way to a #613 Blonde. If you are not coloring the hair you might consider buying a less expensive option if available.
8) Styling: Human Hair extensions generally should not have an issue in styling. The best Virgin hair extensions generally are adaptable to most of the styles.
The above-discussed factors need to be considered when you are purchasing hair extensions, do not make a quick decision until you know what you want. Do proper research before purchasing.