Classic M2 (2mm thread) black hex frame stand-offs. As these are hex shaped stand-offs, they are easy to grip and hold with pliers while tightening the bolts.

6mm – Thread Depth: All the way through
8mm – Thread Depth: All the way through
* The 6 and 8mm ones have a thread which goes all the way through so they can be used as flight stack spacers.

15mm – Thread Depth: 7mm from each end
18mm – Thread Depth: 9mm from each end
20mm – Thread Depth: 9mm from each end
22mm – Thread Depth: 10mm from each end
25mm – Thread Depth: 11mm from each end