If you regularly measure lengths up to 6", you'll want a high quality tool. This brass ruler is one of the best we've ever used.
It features Inches as well as metric scales and a hole for hanging on your pegboard or tying a ribbon/cord for carrying. It is perfectly portable and works great as a bookmark in any notebook, lab journal, or field guide.
The reverse side is blank so you can add any notes you need to recall often or stamp your name into it. The brass is thick enough not to bend, which give the ruler a nice weigh that you'll appreciate.