These aluminum 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.