The RCBS Flash Hole Case Pilot Stop is a caliber-specific tool perfectly suited to use with the RCBS Flash Hole Deburring Tool which helps to reduce case variation. The RCBS Flash Hole Deburring Tool serves to remove excess brass from the flash hole of cases to increase consistency and improve accuracy.When using the RCBS Flash Hole Deburring Tool you need an RCBS Flash Hole Case Pilot Stop to adapt the tool to the specific caliber of the cases you are reloading. The RCBS Flash Hole Case Pilot Stop comes in a variety of sizes to accommodate all of the most popular calibers.