These Tungsten Bucking Bar is a work tool received behind work surfaces to provide a backing member in applying impact fasteners and including intermitted toolhead and handle parts with a low-recoil impact-absorbing spacer provided there between to take shock loads in compression and shear. 
Tungsten Heavy Alloy bucking bars are resulting in a bucking bar of the same weight but half the size. Bucking bars are used in rivet setting to upset the shank of the rivet. Tungsten Heavy Alloy bucking bars reduce the recoil when reflecting the impact back to the rivet shaft.
Higher density reduces vibration and kick back while bucking. Take a cue from the pros and use what they use. We carry a full line of standard bars and can custom build bars to your specifications. All bars have smooth faces and rounded edges and corners for ease and safety in handling.
According to the investigation for different bucking bars of the same shape but different materials and mass characteristics, use of heavier but same sized tungsten bucking can reduce vibration transmission to the hand. 
In a word, tungsten bucking are VERY useful for bucking rivets and will make your life much easier in the build process.