Simple crab gauge. At 100%, it is 5 ¾" inside the tips, which is the legal limit here in Oregon (US). Easily scaled to your local restrictions, 104.3% for 6", and 108.7% for 6 ¼". I added text as negative volume for reference on the scale (see photos). Print in PETG or ASA for outdoor use. Should be fine with just 2 perimeters and .2mm layer height. Please post any questions, comments and makes!