When sourcing Russian hair, the most critical factor is ensuring it is 100% Virgin Slavic Hair. This hair is prized for its fine to medium texture and natural luster. You must verify that the hair is Remi (or Remy) quality, meaning all cuticles are intact and aligned in the same direction to prevent tangling. Look for 'Double Drawn' specifications if your clients require full thickness from root to tip, as opposed to 'Single Drawn' which tapers at the ends. Additionally, ensure the bonding material (for pre-bonded types) uses High-Quality Italian Keratin, which is more durable and less damaging to natural hair.