7A Very porous high-grade remy human hair that can be colored to a medium brown and with proper care last up to 6 months. ~30% of the bundle may have shorter hairs to keep this hair affordable. Recommended care is washing 1-2 per week with deep conditioning after each wash. Air dry and heat styling only after completely dry.
10A Medium porous premium remy human hair that can be colored up to a dark blonde tone. and with proper care last up to 12 months. ~20% of the bundle may have shorter hairs making this a fuller bundle for price. Recommended care is washing once per week with deep conditioning after each wash. Air dry and heat styling only after completely dry.
12A The least porous luxury remy human hair that can be colored up to a light blonde tone. With proper care can last over 12 months. ~15% of the bundle may have shorter hairs making this a full and smooth to the tip. Recommended care is washing once every 2 weeks with deep conditioning after each wash. Air dry and heat styling only after completely dry.
**It is important to remember that short hairs are not the enemy when buying extensions. If all of the hair was 100% the same length it would appear too dense and heavy to look natural. Your extensions should mimic a natural head of hair no matter what the grade of hair is.

Credit Sensationnel.com