We tried several standoff kits before we chose this high quality set as our go-to. The metal hardware threads together cleanly, and the tall standoffs and nuts can be easily attached with your fingers, and then optionally tightened with tools. This 12mm standoff height is the most common spacing for Pi HATs and HAT-compatible boards.
Includes a set of four screws, standoffs, and nuts to secure one add-on board on top of a Pi. See the second image for product dimensions.