These brackets are designed to mount 8mm lead screws to the MakerFarm Pegasus. I have the 10" version with metal motor mounts and X-carriage, so I haven't been able to test it on other sizes, but looking at pictures it should work fine. I'd be interested to hear feedback though.
I originally purchased the ACME Lead Screw Upgrade kit from Colin at MakerFarm but there were a few things I didn't like about it: 1. The provided nut blocks are very snug and don't spin easily, even after over a month of use and running it through a drill as recommended. 2. The Pegasus' X-axis extrusions aren't log enough to mount the nut blocks correctly without the awkward and frustrating extensions. 3. The nut blocks are mounted so low on the X-axis that they nearly hit the motor coupler when the Z-axis is at Z0. This caused some weird Z ringing at lower print heights on my printer since it's hard to get the lead screws perfectly vertical.
This mod uses 8mm brass lead screw nuts to try and fix all of the above. I used these, but there are tons just like it on Amazon and eBay.
If your printer is still using 5mm threaded rods you can still upgrade to lead screws using this mod, you'll just need to source the following: