These are the New Infinite Irons Drop Bottom Plates. The come in 2 types, Liner or Shader. They are made for extra clearance on one inch coil machines. The geometry is perfect for 3/4" diameter coil caps and all the industry standard a-bars we sell. The rear binding post comes off the bottom rear so you have clip cord clearance at the rear of the machine. The 1/4" drop at the tube vise allows for clearance lost when you make a one inch coil machine. You lose tube length and the tube will not go all the way through the tube vise hole.