GigDigit - Square Nut with Set Screw - MP Select Mini V1 - MP Mini Delta (Qty 2)
The “set screw” or “grub screw” that holds the heatbreak and Bowden tube connectors is M3-0.5 x 5mm (6mm will probably work) and takes a 1.5mm Allen wrench or 1/16“ Allen wrench.
The square nut is M3-0.5 It is 5.45mm square and 2.45mm thick.