Biodegradable Plastic Cylinder Molds for single-use applications are non-absorptive and molded as single piece units for dimensional uniformity. Rugged molds have unlimited shelf life and are weather-resistant, but contain a unique additive that allows microbes present in landfills and composting facilities to break down plastic. These 6x12 and 4x8 plastic concrete cylinder molds are unaffected by heat, light or cement paste. Built-in lip helps retain round specimen shape. Writable surface on the cylindrical molds allows recording of data. Tight-fitting Plastic Lids are purchased separately.