Forster Products NTGKIT: Neck Tension Gage (NTG) is used as an inspection tool to quickly and accurately screen/sort a batch of brass before your bullet seating operation. Each NTG provides reloaders with the information needed to create exacting neck tensions during the bullet seating operation. This tool can be used after case neck sizing and before bullet seating to help determine optimal inside neck diameter for consistent release of a bullet from your reloaded rounds. It also allows for inspection of the inside diameters of case necks to be sure a donut has not formed at the neck-shoulder junction. This kit includes five calibers .224, .243, .264, .284, and .308. Each Neck Tension Gage (NTG) Inspection Tool consists of four stepped diameters that increase in size until reaching the handle. Each diameter is etched on the metal tool. Simply insert the stepped end of the tool into the neck of your sized case, sliding it in until one of the diameters achieves a slip fit in the case neck. Use the resulting value to fine-tune your case preparation.