The 6-8 multi-anvil apparatus was introduced by Kawai and Endo using a split steel sphere suspended in pressurized oil, later modified to use the hydraulic ram. In 1990, Walker et al.
Kawai and Endo introduced the 6-8 multi-anvil apparatus, which involved a split steel sphere suspended in pressurized oil. This design was subsequently adapted to utilize a hydraulic ram.  In 1990, Walker et al.