Hornady's Lock-N-Load Bullet Feeder dies are engineered with a twin collet system that ensures reliable feeding of only one bullet at a time for a lifetime of dependable use. The die is case activated and made from high grade solid steel. It comes in a standard 7/8-14 thread which is compatible with any progressive press. Pistol calibers available are 380/ 9mm 357 MAG/38 Special 40 S&W/10mm 44MAG/ 44 Special and 451/452.