They look great, how did you mount them? My base of the rig is 4080
I added similar ones to those (but £10 from eBay) to keep my P1 rig at the same height when I sold the SFX-100. The added mobility for maintenance was a welcome bonus. It's fine to just use two of the bolt holes to connect directly to the underside of the main P1 chassis rails, there were no strength issues at all.Putting my (d.i.y) rig build on these 4" industrial ones.
I have a pack of 4 which came with my monitor stand not sure if there any use? I think there 8mm thread.