Hydrostatic Release UnitMcMurdo Hydrostatic Release for Catagory 1 EPIRB 'BreaktHRU' - the Hydrostatic Release Unit (HRU) Kit from McMurdo. Smaller that other HRUs currently available, BreaktHRU is unique in its use of a small pyrotechnic charge, which is used to enable EPIRBs to automatically float free.Features: