The Pentel Ain Stein Leads are the refill lead from the high-performance family and are stronger and darker than regular leads. Its porous, ceramic cell structure provides regularity of shape and unparalleled strength. There is a designed tube with easy-open rotating lid which is a different shape with eye-catching vivid colours. The Ain Stein leads are super strong and have been made by improving the performance of existing lead in one of its most important features: strength. A ceramic frame holds the lead firmly in place from the inside, that's why we call it super strong lead. In pencil leads, density and strength are usually inversely related. The stronger it gets, the lower the density. The more the blackness, the weaker it gets. Pentel's Ain Stein Lead employs a production method that merges the two properties making a super strong lead.