A-B11729138SM-AI HAMMER-TRIANGULAR .18One New Aftermarket Replacement Triangular Hammer for Simplicity, Murray, and Snapper Chipper Shredders This triangular hammer (also called a flail hammer) is a shredding rotor component used in chipper shredder machines. Mounted on the spinning rotor drum, these hardened hammers pulverize leaves, small branches, and organic debris as material passes through the shredding chamber. The . 18 designation refers to the hammer weight class. The OEM part