The A1 Mini spool holder can be a little short for some spools such as Polymaker spools. This is an adaptation of multiple models made by RedSnapper on Printables and mikelawrencenz on Thingiverse. This new spool holder for the A1 Mini slots into place with friction and allows for wider spools to fit. Probably more importantly though, it allows for the use of a bearing roller which lets the spool glide freely during printing! The stock A1 Mini rod pulls out of the arm when a small locking tab is pushed out of place. Once you have the old one out, slot this one in! It can fit a spool that is 67mm wide.
The bearing pin slides into the open end of the reel. Bearings then slide onto each end of the reel and the reel drops into place in the main spool.
Print the pin and the reel standing up with no supports and the main spool on its side with supports for best results.
For the bearings, it uses Standard size 8 x 22 x 7w bearings which can be purchased here:
https://www.amazon.ca/gp/product/B00WXDAUQG/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1
I hope this works for you!
Cheers,
Brandochili