Limited Run of the Sharps Xtreme Performance Bolt (XPB) Low Mass Bolt Carrier Group. Precisely machined from S7 tool steel. The XPB undergoes a 24-hour thermal cycle proprietary heat treatment and is finished with DLC (Diamond Like Carbon) Coating. Weighs 9.5 ounces. The XPB Carrier Group displays the SRC logo machine cut and visible when the ejection port door is open. The XPB fits standard AR-15/M16/M4 rifles chambered in .223/5.56mm, 25-45 Sharps and 300 Blackout calibers.