I purchased the Marti Michell One-Derful Tumbler Template after frustration with other tumbler rulers. The MM ruler has notches to cut off, in the bottom corners, for lining up. Instead of eyeballing and guessing the offset the notches match up perfectly. The template makes it a little fussier to cut but a snap to sew. Other tumblers do the opposite so... pick your poison.
I have the charm square tumbler from msqc but felt it took too long to fuss, guess and line up the offset; I got very tired of ripping out too. Too much time and fussing for a simple quilt (imho). I recut them with the mm. template and zippy sewed right through the pile. It would be WONDERFUL if msqc would just notch their tumbler rulers; I would buy them all in a second.