Licentia Arms show their LAC Improved Counterweight Kit for use with Night Vision devices... "The Licentia Arms Improved Counterweight Kit is a dual role counterweight system that functions as a night vision counterweight and a secure PVS-31 battery pack holder. Constructed from laser cut laminate Cordura the LAC Improved Counterweight Kit is low profile, has positive retention, offers cable management, and has loop velcro for patches.