C&H Research Mercury Recoil Suppressor. Helps counteract the painful effects of recoil using mercury, one of the heaviest, densest, liquid elements. Compact, permanently sealed steel case is made from bar stock; the only moving part is the liquid mercury so there's no wear, no chance of leaks. Mercury's viscosity varies only 1% from 0 degrees F. to 90 degrees F. which means the recoil-fighting performance is consistent in almost all weather conditions. Fits in rifle or shotgun stocks for easy installation and removal.