Grodan - Gro-Slabs are for the second or third stage of a plant's life. Slabs are available in a variety of sizes and come with instructions on the wrapping. These slabs come in clearly marked biodegradable UV resistant poly sleeves. The poly sleeves have several functions; Comfort in handling. Preventing algae growth. Preventing roots and diseases from moving easily from slab to slab. Minimizing evaporation. Enabling full saturation of the slabs before use. Controlling/directing the water-runoff from the slab