The sachets offer organic and high-grade select tea varietals and herbals. The leaves are larger because they are milled minimally to preserve the natural flavors and bring a richer, deeper flavor to the cup.
The larger leaf stays fresher longer due to its size. Its size slows the process of oxidization and thus depletion of the leaf's aroma and flavors. The flavors of the varietal are then stronger and they release more slowly as you steep. This will result in multiple steeps.