The M2203 is a 1/2 gram desiccant with Silica Gel in a Tyvek pouch. A desiccant remove excess moisture or humidity from packaged goods. A desiccant packaged in Tyvek can absorb up to 40% of its weight in moisture. The desiccant is a silica gel and is chemically inert and non-toxic. Tyvek is a trademarked form of high-density polyethylene. It repels dust and is highly resistant to tears and punctures.