Clear acrylic sample chambers allow easy viewing during test procedure. Two manometer ports are vertically spaced at a distance equal to the chamber diameter. Stainless steel No.100 mesh screen at each port prevents migration of material into the manometer. Porous stones are included with the smaller chambers, while the 6 and 9in (152.4 and 228.6mm) diameter chambers are supplied with brass mesh screens. A compression spring in the top cap applies 5—10lb (2.3—4.5kg) of force to prevent changes in sample density during the test. Anodized aluminum end caps have valves and ports for vacuum and water sources. Tubing is included. Either the HMA-838 Free Standing or HMA-839 Wall Mounted Manometer is required and must be purchased separately. Both feature a 100cm graduated scale and valves. The HMA-836 sliding weight Permeability Compaction Hammer, and HMA-837 Acrylic 1000cc Constant head reservoir with mounting brackets are available as accessories.