They are not tightly packed in, but there are no spacers either. When you pack them as close as you can, there is about a half of a diameter space between two of them.

So, if you have 10 rods for bearings, and you try to jam an 11th one it, the space availabel to do that is only half of what you need.

To make this work, you will need to calculate how many 1/4" or even 3/8" dimeter rods can surround your axel. Just remember to leave an extra .5 diameter so they can roll well.

I assembled mine back in June, so I am going from memory on the sizes.