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.