The Forster Neck Reamer comes in a variety of diameters including .224 .243 .264 .284 .308 .429 and many others. When reloading if the case neck is too thick it can put pressure on the chamber and cause flyers. By mounting this neck reamer in the Case Trimmer rather than the pilot it helps eliminate excess brass from the walls of the neck. This particular neck reamer grinds the entire bullet diameter to precision creating perfect symmetry. Made from strong and durable steel the reamer is designed for unsized and untrimmed fired cases.