These gauges help you determine if the bore of your muzzleloader is in the proper size range to work optimally with our Lock-N-Load Speed Sabot. The Go-Gauge should pass through the bore to the breech plug. Do not force it. If it will not fit, the bore is probably too tight for easy loading. The No-Go Gauge should not fit in the bore at all. If it can be inserted into the bore of the muzzleloader, the bore is probably too loose for optimal accuracy. However, you may find that the sabot will still give satisfactory performance. For use with .50 caliber muzzleloaders.