These tabs are made from 80 lb white offset paper, which is notably heavier and more durable than standard 20lb printer paper, giving them enough rigidity to withstand regular flipping and handling without curling or tearing at the tab edge. For binders opened daily over an extended period, this weight holds up well under normal use; for extremely heavy-handling environments, a mylar-reinforced tab edge offers additional protection beyond what standard 80lb stock provides. If your binder sees only occasional reference use, this weight is more than sufficient without needing reinforcement.