These aluminium hexagonal standoffs are just the right size for mounting expansion PCBs or HATs with standard-size female headers on a Raspberry Pi. The body of each male-female standoff is 11 mm long (dimension L in the mechanical drawing on the right) by 4 mm wide. The male threads extend another 6 mm past the standoff body, and the female threads extend at least 6.35 mm into the body. You can easily screw multiple units together to make longer standoffs. The threads are M2.5 on both ends, since this matches the size of the Raspberry Pi mounting holes. We carry M2.5 nuts and 6 mm M2.5 screws separately.
We also carry 18.6mm-long standoffs that match the height of our extra-tall 2×20 female headers and can be used to mount expansion boards so that they clear all of the components on the Raspberry Pi Model A+ and Model B+ as well as the Raspberry Pi 2 Model B and Raspberry Pi 3 Model B.
In addition to these specialised standoffs, we carry standoffs in a variety of standard imperial lengths and thread types: