The Redding Instant Indicator Headspace and Bullet Comparator is a precision tool used by reloaders to measure headspace and bullet seating depth to the lands. It comes in two versions:With Dial Indicator : Includes a precision dial indicator (usually 0.001" increments). Ready to use out of the box. Allows you to read measurements immediately-ideal for reloaders who don't already have a compatible dial indicator. Typically slightly more expensive due to the included dial. Without Dial Indicator : Does not include the dial indicator - only the base tool insert(s) and stem(s). You must supply your own dial indicator (must be compatible - typically a 0.375" stem diameter). More cost-effective if you already own a dial indicator.