This is a printable replacement for the stock aluminium SC8UU bearing carriers used on many printers, including the Anet A8.
I designed these specifically for the Igus Drylin RJ4JP-01-08 replacements, but the stock LM8UUs will fit just as well. However the problem with the LM8UUs is they are designed for a much higher load than found on most printers and the ball bearings tend to slide rather than roll as they are designed to do, resulting in noise, and wear.
If you go with the Igus Drylins, there's a weight saving of ~37g over the stock SC8UU/LM8UU combination, per unit. That's nearly 150g saved on the y axis of a typical printer.
You will need 4x M4 nuts for each carrier. I used A2 stainless half nuts.
Update: Although these will work fine on the A8, the one that meets with the end switch will miss the switch on some printers, So I've added a lug (as suggested by quualudes). So for printers other than the A8, for the y axis print three plain carriers and one with the lug.
I suggest you print one and check the fit, the bearing should snap in to place and be held just firmly enough that it is not compressed.
If it's too tight, you can reduce the extrusion percentage in your slicer, or on the printer's control panel.
I printed mine with PLA at 190C, fan at 25%.
Push the bearings into the carrier from the top, don't try to slide them in lengthways. They should snap into position, but you might need to slide them a little until they fit over the locator rings.
Push the nuts into the recesses, they should be a little stiff, this is so they don't fall out when you turn them upside down. If necessary, use a screw to pull them into position.
These will work fine on the A8, but as quualudes points out, might not trigger the end stops on some other printers. Check before use! You can find the solution in quualudes' remix
Update: I've added a carrier with a lug, should work on other printers :)