Disclaimer: if you are storing back probes on these, please for the love of god don’t hurt yourself.
Also if you want to add more 4mm banana posts, the ones included are from Ponoma. You can get a pack of 10 from Amazon Or there are some on Aliexpress for little cheaper
Brass inserts: You will notice on the angled holder one of the brass inserts above the center bolt has a small hex retainer. I have that blocked off because the posts are a bit long to fit into that insert (but I still put a brass insert to keep the look consistent). If you want to put a post in there you will need to just remove the little retainer and cut down the threaded banana post to about half the length