Uses M4's will probably need at least 10mm or so, I'd go for 12mm min. you will also need washers
Idk if this is a standard spacing or what, but I just made this to hold my rear light instead of using a meshed together gopro mount that only kinda worked. solid modeling ftw.
I was going to post a link to an amazon listing or something but I cant find it anymore. maybe they stopped making this model. oh well. here it is for you in case you still have yours.
edit: here it is on aliexpress (out of stock) https://www.aliexpress.us/item/3256804238322215.html
The author marked this model as their own original creation.