The Zimmerli Pureness Collection represents an exciting advance in fine men's undergarments. The fabric is 95% Micro Modal and 5% Lycra. Modal is an "organic synthetic" fiber: it is derived from natural cellulose from European beech trees, and then spun into fibers to make this fabric. Unlike inorganic synthetics like polyester or nylon, it has excellent absorbency and breathability characteristics, plus a softness and sheen that make it a distinct pleasure to wear. A touch of Lycra enhances its elasticity and helps it retain its terrific fit throughout the day.