The Bed Load Samplers are designed to sample sand, silt, gravel or rock debris carried by a stream on or immediately above its bed. Bed load materials have particle sizes or a density that doesn’t allow movement far above or for long distances out of contact with the streambed. The standard sampler bags come with a 250-micron mesh size (ASTM specs) made out of nylon for excellent abrasion resistance. Bags can also be provided with 125, 500, and 1000 micron openings as required.