The 4″ (101.6mm) Density Drive Head is used to determine the in-place density of soil by driving a thin-walled tube to obtain a soil sample of known volume. Typically used to verify compacted fill placement, or to obtain samples from the bottom of shallow excavations. The Sampler consists of a zinc plated steel drive head and sliding 10 lb hammer. The drive head is provided with a shock spring to guard against fatigue failure. Meet ASTM D2937. 4″ Drive Tube sold separately.