Compaction Hammer - Std. 5.5 lb.  HM-305
Manual, Moisture/Density Hammer meets ASTM and AASHTO Specs.   It incorporates a 5.5 lb (2.54kg) weight and a drop of 12" (305mm) with a 2" (50.8) face.  Guide sleeve has four vent holes in each end of sleeve to release built-up air pressure.