The Lee Precision 50 BMG Ram Prime is made to specific dimensions for the 50 BMG. It is perfect for the Lee Classic Cast Press. It uses the Lee 50 BMG Shellholder. Other manufacturer's shellholders priming holes may be too small for the diameter of the ram prime. It includes a punch for 50 BMG primers. It works on press upstroke rather than donwstroke for increased leverage and positive primer seating feel.