Guide z-axis for ender 3
One version with bearing 608Z and without.
Guide de l'axe Z pour la ender 3
Une version pour roulement 608Z et sans.
If you like it ;)

T-nut for 20x20 or 20x40 V-Slot aluminum extrusion (6 mm gap) compliant with original metal T-nut but adopted for M3 nut.
There's also a version that fits to #4-40 x 3/16'' nut:https://www.thingiverse.com/thing:3366563
Fits for most of the printers based on V-Slot, e.g. Creality (CR-10, Ender 3, Ender 5), Tevo (Tarantula, Tornado), Tronxy (X1, X3, X5S) and many more
Put it in the profile slot and turn the bolt - it will turn and find its locking position.
Check out my other designs:https://www.thingiverse.com/DaVinci2000/designs
A decent set of M3 hex bolts and nuts can be found on Banggood:https://www.banggood.com/custlink/KG3vEvGOIp