Used to surcharge loads on the soils surface during soaking and penetration. Zinc plated for rust resistance. Weighs 5 lbs. (2.3kg), 5-7/8″ (149mm) OD with a 2-1/8″ (54mm) slot. Used with ASTM D1883 and AASHTO T193 methods. See Also Solid 5lb Surcharge Weight