I use the Wilson trimmer with the micrometer feature. It's a piece of high quality precision kit, and only slightly more expensive that the Lyman or RCBS. Tremendous accuracy trimming cases to uncanny consistent length and squareness and much faster to set up than the Lyman or RCBS. I liked the Wilson so much it became the only tool I'd ever consider for hand trimming brass, and subsequently sold off both my Lyman and RCBS trimmers. It is so good in fact that you can quickly set up the trim length for the 1st piece of brass, verify the 1st cut case with your dial micrometer (to make yourself feel good), and just do the rest of the run of brass with full confidence that the trim length difference between cases will be unmeasurable as previously posted. It is slower to measure each piece of brass to see if it needs trimming, so I just go ahead and cut the bunch once I set up the trim length for the 1st case. The Wilson is THE be-all end-all last word in hand trimming. For power trimming, get a Gracey. The Gracey is a PITA to set up, but will trim 10,000 pieces of brass as fast as you can push feed them into the trimmer..... works like a garburetor or wood chipper, but does a very accurate job of high volume trimming of brass.