ONNIT Steel Mace - Perfectly Balanced Hand-Sculpted Cast Iron Disproportionate weight displacement optimizes stabilizer muscles, joints and primary power centers. Excellent training for sports that require rotational core strength and shoulder mobility, such as mixed martial arts, boxing, brazilian jiu-jitsu, and more. Originally developed by the Persian Warrior Elite for real world combat and wrestling. Only a light weight is needed to give yourself a tremendous workout, making this tool great for home gyms.