This item is inaccurate. I measured several headspace gauges and bore erosion gauges, taking multiple measurements from each, and I was always slightly off. I double checked all the same items with different sets of calipers, both dial and digital, and they were all on the money with the exact measurements expected from each item. Considering that all the others I tried were fairly inexpensive (maybe $20 to $50 max), I cannot rate this item above two stars. You can spend a similar amount of money and get something that is more accurate.